diff --git a/includes/common.inc b/includes/common.inc
index 34fa9b9..2836c49 100644
--- a/includes/common.inc
+++ b/includes/common.inc
@@ -232,6 +232,30 @@ function drupal_get_profile() {
   return $profile;
 }
 
+/**
+ * Returns an array of the installation profile hierarchy.
+ *
+ * @return $profiles
+ *   An array of installation profiles.
+ */
+function drupal_get_profiles() {
+  global $install_state;
+
+  if (!empty($install_state['profiles'])) {
+    $profiles = $install_state['profiles'];
+  }
+  else {
+    $profiles = variable_get('install_profiles', array(drupal_get_profile()));
+  }
+  while(list($key, $profile) = each($profiles)) {
+    $path = drupal_get_path('profile', $profile) . '/' . $profile . '.info';
+    $info = drupal_parse_info_file($path);
+    if (!empty($info['base profile'])) {
+      $profiles[] = $info['base profile'];
+    }
+  }
+  return $profiles;
+}
 
 /**
  * Sets the breadcrumb trail for the current page.
@@ -5480,25 +5504,26 @@ function drupal_system_listing($mask, $directory, $key = 'name', $min_depth = 1)
 
   $searchdir = array($directory);
   $files = array();
-
+  $installed_profiles = array_reverse(drupal_get_profiles());
   // The 'profiles' directory contains pristine collections of modules and
   // themes as organized by a distribution. It is pristine in the same way
   // that /modules is pristine for core; users should avoid changing anything
   // there in favor of sites/all or sites/<domain> directories.
   $profiles = array();
-  $profile = drupal_get_profile();
   // For SimpleTest to be able to test modules packaged together with a
   // distribution we need to include the profile of the parent site (in which
   // test runs are triggered).
   if (drupal_valid_test_ua()) {
     $testing_profile = variable_get('simpletest_parent_profile', FALSE);
-    if ($testing_profile && $testing_profile != $profile) {
+    if ($testing_profile && !in_array($testing_profile, $installed_profiles)) {
       $profiles[] = $testing_profile;
     }
   }
   // In case both profile directories contain the same extension, the actual
   // profile always has precedence.
-  $profiles[] = $profile;
+
+  $profiles = array_merge($profiles, $installed_profiles);
+
   foreach ($profiles as $profile) {
     if (file_exists("profiles/$profile/$directory")) {
       $searchdir[] = "profiles/$profile/$directory";
diff --git a/includes/install.core.inc b/includes/install.core.inc
index ad43b42..1b80cf6 100644
--- a/includes/install.core.inc
+++ b/includes/install.core.inc
@@ -162,8 +162,10 @@ function install_state_defaults() {
     // An array of information about the chosen installation profile. This will
     // be filled in based on the profile's .info file.
     'profile_info' => array(),
-    // An array of available installation profiles.
+    // An array of the profile hiearchy.
     'profiles' => array(),
+    // An array of available installation profiles.
+    'profiles_available' => array(),
     // An array of server variables that will be substituted into the global
     // $_SERVER array via drupal_override_server_variables(). Used by
     // non-interactive installations only.
@@ -531,14 +533,14 @@ function install_tasks($install_state) {
   $tasks = array(
     'install_select_profile' => array(
       'display_name' => st('Choose profile'),
-      'display' => count($install_state['profiles']) != 1,
+      'display' => count($install_state['profiles_available']) != 1,
       'run' => INSTALL_TASK_RUN_IF_REACHED,
     ),
-    'install_select_locale' => array(
-      'display_name' => st('Choose language'),
+    'install_load_profile' => array(
       'run' => INSTALL_TASK_RUN_IF_REACHED,
     ),
-    'install_load_profile' => array(
+    'install_select_locale' => array(
+      'display_name' => st('Choose language'),
       'run' => INSTALL_TASK_RUN_IF_REACHED,
     ),
     'install_verify_requirements' => array(
@@ -555,7 +557,7 @@ function install_tasks($install_state) {
       'run' => INSTALL_TASK_RUN_IF_REACHED,
     ),
     'install_profile_modules' => array(
-      'display_name' => count($install_state['profiles']) == 1 ? st('Install site') : st('Install profile'),
+      'display_name' => count($install_state['profiles_available']) == 1 ? st('Install site') : st('Install profile'),
       'type' => 'batch',
     ),
     'install_import_locales' => array(
@@ -570,19 +572,21 @@ function install_tasks($install_state) {
     ),
   );
 
-  // Now add any tasks defined by the installation profile.
-  if (!empty($install_state['parameters']['profile'])) {
-    // Load the profile install file, because it is not always loaded when
-    // hook_install_tasks() is invoked (e.g. batch processing).
-    $profile_install_file = DRUPAL_ROOT . '/profiles/' . $install_state['parameters']['profile'] . '/' . $install_state['parameters']['profile'] . '.install';
-    if (file_exists($profile_install_file)) {
-      include_once $profile_install_file;
-    }
-    $function = $install_state['parameters']['profile'] . '_install_tasks';
-    if (function_exists($function)) {
-      $result = $function($install_state);
-      if (is_array($result)) {
-        $tasks += $result;
+  // Now add any tasks defined by the installation profiles.
+  if (!empty($install_state['profiles'])) {
+    $profiles = array_reverse($install_state['profiles']);
+    foreach ($profiles as $profile) {
+      $profile_install_file = DRUPAL_ROOT . '/profiles/' . $profile . '/' . $profile . '.install';
+      if (file_exists($profile_install_file)) {
+        include_once $profile_install_file;
+      }
+
+      $function = $profile . '_install_tasks';
+      if (function_exists($function)) {
+        $result = $function($install_state);
+        if (is_array($result)) {
+          $tasks += $result;
+        }
       }
     }
   }
@@ -600,14 +604,17 @@ function install_tasks($install_state) {
     ),
   );
 
-  // Allow the installation profile to modify the full list of tasks.
-  if (!empty($install_state['parameters']['profile'])) {
-    $profile_file = DRUPAL_ROOT . '/profiles/' . $install_state['parameters']['profile'] . '/' . $install_state['parameters']['profile'] . '.profile';
-    if (file_exists($profile_file)) {
-      include_once $profile_file;
-      $function = $install_state['parameters']['profile'] . '_install_tasks_alter';
-      if (function_exists($function)) {
-        $function($tasks, $install_state);
+  // Allow for the installation profiles to modify the full list of tasks.
+  if (!empty($install_state['profiles'])) {
+    $profiles = array_reverse($install_state['profiles']);
+    foreach ($profiles as $profile) {
+      $profile_file = DRUPAL_ROOT . '/profiles/' . $profile . '/' . $profile . '.profile';
+      if (file_exists($profile_file)) {
+        include_once $profile_file;
+        $function = $profile . '_install_tasks_alter';
+        if (function_exists($function)) {
+          $function($tasks, $install_state);
+        }
       }
     }
   }
@@ -801,11 +808,26 @@ function install_system_module(&$install_state) {
 
   // Save the list of other modules to install for the upcoming tasks.
   // variable_set() can be used now that system.module is installed.
-  $modules = $install_state['profile_info']['dependencies'];
+  $modules = array();
+  $profiles = array($install_state['parameters']['profile']);
+  $profile_info = $install_state['profile_info'];
+  do {
+    $modules = array_merge($modules, $profile_info['dependencies']);
+    if (!empty($profile_info['base profile']) && isset($profile_info[$profile_info['base profile']])) {
+      $profiles[] = $profile_info['base profile'];
+      $profile_info = $profile_info[$profile_info['base profile']];
+    }
+    else {
+      $profile_info = NULL;
+    }
+  }
+  while ($profile_info);
 
   // The installation profile is also a module, which needs to be installed
   // after all the dependencies have been installed.
-  $modules[] = drupal_get_profile();
+  foreach ($profiles as $profile) {
+    $modules[] = $profile;
+  }
 
   variable_set('install_profile_modules', array_diff($modules, array('system')));
   $install_state['database_tables_exist'] = TRUE;
@@ -1043,10 +1065,10 @@ function install_find_profiles() {
  *   thrown if a profile cannot be chosen automatically.
  */
 function install_select_profile(&$install_state) {
-  $install_state['profiles'] += install_find_profiles();
+  $install_state['profiles_available'] += install_find_profiles();
   if (empty($install_state['parameters']['profile'])) {
     // Try to find a profile.
-    $profile = _install_select_profile($install_state['profiles']);
+    $profile = _install_select_profile($install_state['profiles_available']);
     if (empty($profile)) {
       // We still don't have a profile, so display a form for selecting one.
       // Only do this in the case of interactive installations, since this is
@@ -1056,7 +1078,7 @@ function install_select_profile(&$install_state) {
       if ($install_state['interactive']) {
         include_once DRUPAL_ROOT . '/includes/form.inc';
         drupal_set_title(st('Select an installation profile'));
-        $form = drupal_get_form('install_select_profile_form', $install_state['profiles']);
+        $form = drupal_get_form('install_select_profile_form', $install_state['profiles_available']);
         return drupal_render($form);
       }
       else {
@@ -1223,9 +1245,14 @@ function install_find_locales($profilename) {
  *   locale cannot be chosen automatically.
  */
 function install_select_locale(&$install_state) {
+  $locales = array();
+  $profiles = array_reverse($install_state['profiles']);
   // Find all available locales.
-  $profilename = $install_state['parameters']['profile'];
-  $locales = install_find_locales($profilename);
+  foreach ($profiles as $profile) {
+    $profilelocales = install_find_locales($profile);
+    $locales = array_merge($locales, $profilelocales);
+  }
+  $locales = array_unique($locales, SORT_REGULAR);
   $install_state['locales'] += $locales;
 
   if (!empty($_POST['locale'])) {
@@ -1237,6 +1264,7 @@ function install_select_locale(&$install_state) {
     }
   }
 
+  $profilename = $install_state['parameters']['profile'];
   if (empty($install_state['parameters']['locale'])) {
     // If only the built-in (English) language is available, and we are
     // performing an interactive installation, inform the user that the
@@ -1276,14 +1304,16 @@ function install_select_locale(&$install_state) {
     }
     else {
       // Allow profile to pre-select the language, skipping the selection.
-      $function = $profilename . '_profile_details';
-      if (function_exists($function)) {
-        $details = $function();
-        if (isset($details['language'])) {
-          foreach ($locales as $locale) {
-            if ($details['language'] == $locale->name) {
-              $install_state['parameters']['locale'] = $locale->name;
-              return;
+      foreach ($profiles as $profile) {
+        $function = $profile . '_profile_details';
+        if (function_exists($function)) {
+          $details = $function();
+          if (isset($details['language'])) {
+            foreach ($locales as $locale) {
+              if ($details['language'] == $locale->name) {
+                $install_state['parameters']['locale'] = $locale->name;
+                return;
+              }
             }
           }
         }
@@ -1371,10 +1401,25 @@ function install_load_profile(&$install_state) {
   $profile_file = DRUPAL_ROOT . '/profiles/' . $install_state['parameters']['profile'] . '/' . $install_state['parameters']['profile'] . '.profile';
   if (file_exists($profile_file)) {
     include_once $profile_file;
-    $install_state['profile_info'] = install_profile_info($install_state['parameters']['profile'], $install_state['parameters']['locale']);
+    $install_state['profiles'][] = $install_state['parameters']['profile'];
+    $install_state['profile_info'] = install_profile_info($install_state['parameters']['profile']);
+    $profile_info = &$install_state['profile_info'];
+    while (isset($profile_info['base profile']) && $profile_info['base profile']) {
+      $profile = $profile_info['base profile'];
+      $profile_file = DRUPAL_ROOT . '/profiles/' . $profile . '/' . $profile . '.profile';
+      if (file_exists($profile_file)) {
+        include_once $profile_file;
+        $install_state['profiles'][] = $profile;
+        $profile_info[$profile] = install_profile_info($profile);
+        $profile_info = &$profile_info[$profile];
+      }
+      else {
+        throw new Exception(install_no_profile_error());
+      }
+    }
   }
   else {
-    throw new Exception(st('Sorry, the profile you have chosen cannot be loaded.'));
+    throw new Exception(install_no_profile_error());
   }
 }
 
@@ -1409,7 +1454,10 @@ function install_profile_modules(&$install_state) {
   // Although the profile module is marked as required, it needs to go after
   // every dependency, including non-required ones. So clear its required
   // flag for now to allow it to install late.
-  $files[$install_state['parameters']['profile']]->info['required'] = FALSE;
+  foreach ($install_state['profiles'] as $profile) {
+    $files[$profile]->info['required'] = FALSE;
+  }
+
   // Add modules that other modules depend on.
   foreach ($modules as $module) {
     if ($files[$module]->requires) {
@@ -1570,13 +1618,19 @@ function install_finished(&$install_state) {
 
   // Remember the profile which was used.
   variable_set('install_profile', drupal_get_profile());
+  variable_set('install_profiles', drupal_get_profiles());
 
   // Installation profiles are always loaded last
-  db_update('system')
-    ->fields(array('weight' => 1000))
-    ->condition('type', 'module')
-    ->condition('name', drupal_get_profile())
-    ->execute();
+  $profiles = drupal_get_profiles();
+  $weight = 1000 + count($profiles);
+  foreach ($profiles as $profile) {
+    db_update('system')
+      ->fields(array('weight' => $weight))
+      ->condition('type', 'module')
+      ->condition('name', $profile)
+      ->execute();
+    $weight = $weight - 1;
+  }
 
   // Cache a fully-built schema.
   drupal_get_schema(NULL, TRUE);
@@ -1619,10 +1673,12 @@ function _install_profile_modules_finished($success, $results, $operations) {
  * Checks installation requirements and reports any errors.
  */
 function install_check_requirements($install_state) {
-  $profile = $install_state['parameters']['profile'];
+  $requirements = array();
 
   // Check the profile requirements.
-  $requirements = drupal_check_profile($profile);
+  foreach ($install_state['profiles'] as $profile) {
+    $requirements += drupal_check_profile($profile);
+  }
 
   // If Drupal is not set up already, we need to create a settings file.
   if (!$install_state['settings_verified']) {
diff --git a/includes/install.inc b/includes/install.inc
index 2b55589..f0d4336 100644
--- a/includes/install.inc
+++ b/includes/install.inc
@@ -676,31 +676,62 @@ function drupal_rewrite_settings($settings = array(), $prefix = '') {
  *   The list of modules to install.
  */
 function drupal_verify_profile($install_state) {
-  $profile = $install_state['parameters']['profile'];
+  $profiles = $install_state['profiles'];
   $locale = $install_state['parameters']['locale'];
 
   include_once DRUPAL_ROOT . '/includes/file.inc';
   include_once DRUPAL_ROOT . '/includes/common.inc';
 
-  $profile_file = DRUPAL_ROOT . "/profiles/$profile/$profile.profile";
-
-  if (!isset($profile) || !file_exists($profile_file)) {
+  if (!empty($profiles)) {
+    foreach ($profiles as $profile) {
+      $profile_file = DRUPAL_ROOT . '/profiles/' . $profile . '/' . $profile . '.profile';
+      if (!file_exists($profile_file)) {
+        throw new Exception(install_no_profile_error());
+      }
+    }
+  }
+  else {
     throw new Exception(install_no_profile_error());
   }
+
   $info = $install_state['profile_info'];
+  $profile_dependencies = $info['dependencies'];
+
+  while (isset($info['base profile']) && $info[$info['base profile']]) {
+    $info = $info[$info['base profile']];
+    $profile_dependencies += $info['dependencies'];
+  }
 
   // Get a list of modules that exist in Drupal's assorted subdirectories.
   $present_modules = array();
   foreach (drupal_system_listing('/^' . DRUPAL_PHP_FUNCTION_PATTERN . '\.module$/', 'modules', 'name', 0) as $present_module) {
-    $present_modules[] = $present_module->name;
+    $present_module_path = drupal_get_path('module', $present_module->name);
+    $present_modules[$present_module->name] = drupal_parse_info_file($present_module_path . '/' . $present_module->name . '.info');
   }
 
-  // The installation profile is also a module, which needs to be installed
-  // after all the other dependencies have been installed.
-  $present_modules[] = drupal_get_profile();
+  $dependencies = array();
+  // Recursively seek all dependencies; not just those of the profiles.
+  foreach ($profile_dependencies as $profile_dependency) {
+    _drupal_verify_profile_dependencies($dependencies, $profile_dependency);
+  }
 
   // Verify that all of the profile's required modules are present.
-  $missing_modules = array_diff($info['dependencies'], $present_modules);
+  $missing_modules = array();
+  foreach ($dependencies as $dependency) {
+    // Check early if the module even exists, continue early on.
+    if (!empty($present_modules[$dependency['name']])) {
+      // Check for version match if a versioned module
+      if (isset($present_modules[$dependency['name']]['version'])) {
+        $current_version = str_replace(DRUPAL_CORE_COMPATIBILITY . '-', '', $present_modules[$dependency['name']]['version']);
+        if ($incompatible = drupal_check_incompatibility($dependency, $current_version)) {
+          $missing_modules[] = $dependency['name'] . $incompatible;
+        }
+      }
+    }
+    else {
+      $missing_modules[] = $dependency['name'];
+    }
+  }
 
   $requirements = array();
 
@@ -720,6 +751,55 @@ function drupal_verify_profile($install_state) {
 }
 
 /**
+ * Recursively load all profile dependencies.
+ *
+ * This helper function recursively loads and searches all of the
+ * $module's dependencies and appends them to the $dependencies.
+ *
+ * @param array $dependencies
+ *   An array passed by reference in which dependencies are appended.
+ * @param $module
+ *   The module name to load dependencies for.
+ */
+function _drupal_verify_profile_dependencies(array &$dependencies, $module) {
+  if (isset($dependencies[$module])) {
+    // Exit early if $module already has been checked.
+    return;
+  }
+
+  $module_info_file = drupal_get_path('module', $module) . '/' . $module . '.info';
+  if (file_exists($module_info_file)) {
+    $module_info = drupal_parse_info_file($module_info_file);
+    if (!empty($module_info['dependencies'])) {
+      foreach ($module_info['dependencies'] as $dependency) {
+        $dependency = drupal_parse_dependency($dependency);
+        if (empty($dependency['versions'])) {
+          // Create default versions array in case no versions
+          // were found while parsing dependency.
+          $dependency['versions'] = array();
+        }
+
+        if (isset($dependencies[$dependency['name']])) {
+          $dependencies[$dependency['name']]['versions'] = array_merge($dependencies[$dependency['name']]['versions'], $dependency['versions']);
+        }
+        else {
+          $dependencies[$dependency['name']] = $dependency;
+        }
+
+        // Recursively call this function one self.
+        _drupal_verify_profile_dependencies($dependencies, $dependency['name']);
+      }
+    }
+  }
+  else {
+    $dependencies[$module] = array(
+      'name' => $module,
+      'versions' => array(),
+    );
+  }
+}
+
+/**
  * Installs the system module.
  *
  * Separated from the installation of other modules so core system
@@ -1293,6 +1373,7 @@ function install_profile_info($profile, $locale = 'en') {
       'dependencies' => array(),
       'description' => '',
       'distribution_name' => 'Drupal',
+      'base profile' => NULL,
       'version' => NULL,
       'hidden' => FALSE,
       'php' => DRUPAL_MINIMUM_PHP,
diff --git a/modules/system/system.module b/modules/system/system.module
index 39de758..d665c2f 100644
--- a/modules/system/system.module
+++ b/modules/system/system.module
@@ -2369,14 +2369,20 @@ function _system_rebuild_module_data() {
   $modules = drupal_system_listing('/^' . DRUPAL_PHP_FUNCTION_PATTERN . '\.module$/', 'modules', 'name', 0);
 
   // Include the installation profile in modules that are loaded.
-  $profile = drupal_get_profile();
-  $modules[$profile] = new stdClass();
-  $modules[$profile]->name = $profile;
-  $modules[$profile]->uri = 'profiles/' . $profile . '/' . $profile . '.profile';
-  $modules[$profile]->filename = $profile . '.profile';
+  $profiles = drupal_get_profiles();
+  $weight = 1000 + count($profiles);
+
+  foreach ($profiles as $profile) {
+    $modules[$profile] = new stdClass();
+    $modules[$profile]->name = $profile;
+    $modules[$profile]->uri = 'profiles/' . $profile . '/' . $profile . '.profile';
+    $modules[$profile]->filename = $profile . '.profile';
+
+    // Installation profile hooks are always executed last.
+    $modules[$profile]->weight = $weight;
+    $weight = $weight - 1;
+  }
 
-  // Installation profile hooks are always executed last.
-  $modules[$profile]->weight = 1000;
 
   // Set defaults for module info.
   $defaults = array(
@@ -2436,7 +2442,11 @@ function _system_rebuild_module_data() {
     drupal_alter('system_info', $modules[$key]->info, $modules[$key], $type);
   }
 
-  if (isset($modules[$profile])) {
+  foreach ($profiles as $profile) {
+    if (!isset($modules[$profile])) {
+      continue;
+    }
+
     // The installation profile is required, if it's a valid module.
     $modules[$profile]->info['required'] = TRUE;
     // Add a default distribution name if the profile did not provide one. This