diff --git a/includes/common.inc b/includes/common.inc
index 44ff460787..6e2ea9da8a 100644
--- a/includes/common.inc
+++ b/includes/common.inc
@@ -232,6 +232,26 @@ function drupal_get_profile() {
   return $profile;
 }
 
+/**
+ * Returns a list of related install profiles in decending order of their
+ * dependencies.
+ *
+ * @return $profiles
+ *   An array of installation profiles.
+ */
+function drupal_get_profiles() {
+  $profile = drupal_get_profile();
+  $info = drupal_parse_info_file("profiles/$profile/$profile.info");
+
+  $profiles = array($profile);
+  while (!empty($info) && isset($info['base profile'])) {
+    $profiles[] = $info['base profile'];
+    $profile = $info['base profile'];
+    $info = drupal_parse_info_file("profiles/$profile/$profile.info");
+  }
+  $profiles = array_reverse($profiles);
+  return $profiles;
+}
 
 /**
  * Sets the breadcrumb trail for the current page.
@@ -5566,7 +5586,7 @@ function drupal_system_listing($mask, $directory, $key = 'name', $min_depth = 1)
   }
   // In case both profile directories contain the same extension, the actual
   // profile always has precedence.
-  $profiles[] = $profile;
+  $profiles = array_merge($profiles, drupal_get_profiles());
   foreach ($profiles as $profile) {
     if (file_exists("profiles/$profile/$directory")) {
       $searchdir[] = "profiles/$profile/$directory";
diff --git a/includes/install.core.inc b/includes/install.core.inc
index b18d23d213..6b4acc11be 100644
--- a/includes/install.core.inc
+++ b/includes/install.core.inc
@@ -162,6 +162,9 @@ function install_state_defaults() {
     // An array of information about the chosen installation profile. This will
     // be filled in based on the profile's .info file.
     'profile_info' => array(),
+    // An array of information for each of the base profiles of the chosen
+    // install profile.
+    'base_profiles_info' => array(),
     // An array of available installation profiles.
     'profiles' => array(),
     // An array of server variables that will be substituted into the global
@@ -574,15 +577,17 @@ function install_tasks($install_state) {
   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;
+    foreach (drupal_get_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 += $result;
+        }
       }
     }
   }
@@ -602,12 +607,14 @@ function install_tasks($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);
+    foreach (drupal_get_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, $install_state);
+        }
       }
     }
   }
@@ -801,11 +808,19 @@ function install_system_module(&$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'];
+  $profiles = drupal_get_profiles();
+  $profile_dependencies = array();
+
+  foreach ($profiles as $profile) {
+    $info = install_profile_info($profile);
+    $profile_dependencies = array_unique(array_merge($profile_dependencies, $info['dependencies']));
+  }
+
+  $modules = $profile_dependencies;
 
   // The installation profile is also a module, which needs to be installed
   // after all the dependencies have been installed.
-  $modules[] = drupal_get_profile();
+  $modules = array_merge($modules, $profiles);
 
   variable_set('install_profile_modules', array_diff($modules, array('system')));
   $install_state['database_tables_exist'] = TRUE;
@@ -1231,8 +1246,15 @@ function install_find_locales($profilename) {
  */
 function install_select_locale(&$install_state) {
   // Find all available locales.
+  $locales = array();
   $profilename = $install_state['parameters']['profile'];
-  $locales = install_find_locales($profilename);
+
+  // @todo remove duplicate 'en' languages from install_find_locales() to avoid
+  // polluting the 'locales' install state key.
+  foreach (drupal_get_profiles() as $profile) {
+    $locales = array_merge($locales, install_find_locales($profile));
+  }
+
   $install_state['locales'] += $locales;
 
   if (!empty($_POST['locale'])) {
@@ -1375,13 +1397,21 @@ function install_already_done_error() {
  *   the profile cannot be loaded.
  */
 function install_load_profile(&$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']);
-  }
-  else {
-    throw new Exception(st('Sorry, the profile you have chosen cannot be loaded.'));
+  foreach (drupal_get_profiles() as $profile) {
+    $profile_file = DRUPAL_ROOT . "/profiles/$profile/$profile.profile";
+    if (file_exists($profile_file)) {
+      include_once $profile_file;
+
+      if ($install_state['parameters']['profile'] == $profile) {
+        $install_state['profile_info'] = install_profile_info($profile, $install_state['parameters']['locale']);
+      }
+      else {
+        $install_state['base_profiles_info'][] = install_profile_info($profile, $install_state['parameters']['locale']);
+      }
+    }
+    else {
+      throw new Exception(st('Sorry, the profile you have chosen cannot be loaded.'));
+    }
   }
 }
 
@@ -1416,7 +1446,9 @@ 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 (drupal_get_profiles() as $profile) {
+    $files[$profile]->info['required'] = FALSE;
+  }
   // Add modules that other modules depend on.
   foreach ($modules as $module) {
     if ($files[$module]->requires) {
@@ -1577,6 +1609,10 @@ function install_finished(&$install_state) {
 
   // Remember the profile which was used.
   variable_set('install_profile', drupal_get_profile());
+  // When sub-profiles are used, remember the dependency tree.
+  if ($profiles = drupal_get_profiles()) {
+    variable_set('install_profiles', $profiles);
+  }
 
   // Installation profiles are always loaded last
   db_update('system')
diff --git a/includes/install.inc b/includes/install.inc
index b7db783586..a425ccb480 100644
--- a/includes/install.inc
+++ b/includes/install.inc
@@ -676,15 +676,28 @@ function drupal_rewrite_settings($settings = array(), $prefix = '') {
  *   The list of modules to install.
  */
 function drupal_verify_profile($install_state) {
-  $profile = $install_state['parameters']['profile'];
+  $selected_profile = $install_state['parameters']['profile'];
   $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";
+  $profiles = drupal_get_profiles();
 
-  if (!isset($profile) || !file_exists($profile_file)) {
+  if (!empty($profiles)) {
+    $profile_dependencies = array();
+
+    foreach ($profiles as $profile) {
+      $profile_file = DRUPAL_ROOT . "/profiles/$profile/$profile.profile";
+
+      if (!file_exists($profile_file)) {
+        throw new Exception(install_no_profile_error());
+      }
+      $info = install_profile_info($profile);
+      $profile_dependencies = array_unique(array_merge($profile_dependencies, $info['dependencies']));
+    }
+  }
+  else {
     throw new Exception(install_no_profile_error());
   }
   $info = $install_state['profile_info'];
@@ -697,10 +710,10 @@ function drupal_verify_profile($install_state) {
 
   // 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();
+  $present_modules = array_merge($present_modules, $profiles);
 
   // Verify that all of the profile's required modules are present.
-  $missing_modules = array_diff($info['dependencies'], $present_modules);
+  $missing_modules = array_diff($profile_dependencies, $present_modules);
 
   $requirements = array();
 
@@ -778,7 +791,7 @@ function drupal_uninstall_modules($module_list = array(), $uninstall_dependents
     // Create an associative array with weights as values.
     $module_list = array_flip(array_values($module_list));
 
-    $profile = drupal_get_profile();
+    $profiles = drupal_get_profiles();
     foreach (array_keys($module_list) as $module) {
       if (!isset($module_data[$module]) || drupal_get_installed_schema_version($module) == SCHEMA_UNINSTALLED) {
         // This module doesn't exist or is already uninstalled. Skip it.
@@ -792,7 +805,7 @@ function drupal_uninstall_modules($module_list = array(), $uninstall_dependents
       // them automatically because uninstalling a module is a destructive
       // operation.
       foreach (array_keys($module_data[$module]->required_by) as $dependent) {
-        if (!isset($module_list[$dependent]) && drupal_get_installed_schema_version($dependent) != SCHEMA_UNINSTALLED && $dependent != $profile) {
+        if (!isset($module_list[$dependent]) && drupal_get_installed_schema_version($dependent) != SCHEMA_UNINSTALLED && !in_array($dependent, $profiles)) {
           return FALSE;
         }
       }
@@ -1131,7 +1144,12 @@ function st($string, array $args = array(), array $options = array()) {
       // with its name ending in {$install_state['parameters']['locale']}.po
       // This might or might not be the entire filename. It is also possible
       // that multiple files end with the same extension, even if unlikely.
-      $po_files = file_scan_directory('./profiles/' . $install_state['parameters']['profile'] . '/translations', '/'. $install_state['parameters']['locale'] .'\.po$/', array('recurse' => FALSE));
+      $po_files = array();
+
+      foreach (drupal_get_profiles() as $profile) {
+        $locales = file_scan_directory('./profiles/' . $profile . '/translations', '/'. $install_state['parameters']['locale'] .'\.po$/', array('recurse' => FALSE));
+        $po_files = array_merge($po_files, $locales);
+      }
       if (count($po_files)) {
         require_once DRUPAL_ROOT . '/includes/locale.inc';
         foreach ($po_files as $po_file) {
@@ -1171,24 +1189,36 @@ function st($string, array $args = array(), array $options = array()) {
  */
 function drupal_check_profile($profile) {
   include_once DRUPAL_ROOT . '/includes/file.inc';
+  $requirements = array();
 
-  $profile_file = DRUPAL_ROOT . "/profiles/$profile/$profile.profile";
+  if (isset($profile)) {
+    $profile_dependencies = array();
 
-  if (!isset($profile) || !file_exists($profile_file)) {
-    throw new Exception(install_no_profile_error());
-  }
+    // Loop through all active install profiles to collect dependencies.
+    foreach (drupal_get_profiles() as $profile) {
+      $profile_file = DRUPAL_ROOT . "/profiles/$profile/$profile.profile";
 
-  $info = install_profile_info($profile);
+      if (!file_exists($profile_file)) {
+        throw new Exception(install_no_profile_error());
+      }
 
-  // Collect requirement testing results.
-  $requirements = array();
-  foreach ($info['dependencies'] as $module) {
-    module_load_install($module);
-    $function = $module . '_requirements';
-    if (function_exists($function)) {
-      $requirements = array_merge($requirements, $function('install'));
+      $info = install_profile_info($profile);
+      $profile_dependencies = array_unique(array_merge($profile_dependencies, $info['dependencies']));
+    }
+
+    // Collect requirement testing results.
+    foreach ($profile_dependencies as $module) {
+      module_load_install($module);
+      $function = $module . '_requirements';
+      if (function_exists($function)) {
+        $requirements = array_merge($requirements, $function('install'));
+      }
     }
   }
+  else {
+    throw new Exception(install_no_profile_error());
+  }
+
   return $requirements;
 }
 
diff --git a/includes/module.inc b/includes/module.inc
index 4c2b3fbeeb..96758de9cb 100644
--- a/includes/module.inc
+++ b/includes/module.inc
@@ -543,7 +543,7 @@ function module_disable($module_list, $disable_dependents = TRUE) {
     // Create an associative array with weights as values.
     $module_list = array_flip(array_values($module_list));
 
-    $profile = drupal_get_profile();
+    $profiles = drupal_get_profiles();
     // The array is iterated over manually (instead of using a foreach) because
     // modules may be added to the list within the loop and we need to process
     // them.
@@ -559,7 +559,7 @@ function module_disable($module_list, $disable_dependents = TRUE) {
       // Add dependent modules to the list, with a placeholder weight.
       // The new modules will be processed as the while loop continues.
       foreach ($module_data[$module]->required_by as $dependent => $dependent_data) {
-        if (!isset($module_list[$dependent]) && $dependent != $profile) {
+        if (!isset($module_list[$dependent]) && !in_array($dependent, $profiles)) {
           $module_list[$dependent] = 0;
         }
       }
@@ -987,7 +987,7 @@ function drupal_required_modules() {
   $required = array();
 
   // An installation profile is required and one must always be loaded.
-  $required[] = drupal_get_profile();
+  $required = array_merge($required, drupal_get_profiles());
 
   foreach ($files as $name => $file) {
     $info = drupal_parse_info_file($file->uri);
diff --git a/modules/simpletest/drupal_web_test_case.php b/modules/simpletest/drupal_web_test_case.php
index a0872c234a..52aabbaa4e 100644
--- a/modules/simpletest/drupal_web_test_case.php
+++ b/modules/simpletest/drupal_web_test_case.php
@@ -1520,10 +1520,16 @@ class DrupalWebTestCase extends DrupalTestCase {
 
     // Include the testing profile.
     variable_set('install_profile', $this->profile);
-    $profile_details = install_profile_info($this->profile, 'en');
 
     // Install the modules specified by the testing profile.
-    module_enable($profile_details['dependencies'], FALSE);
+    $profiles = drupal_get_profiles();
+    $profile_dependencies = array();
+
+    foreach ($profiles as $profile) {
+      $info = install_profile_info($profile);
+      $profile_dependencies = array_unique(array_merge($profile_dependencies, $info['dependencies']));
+    }
+    module_enable($profile_dependencies);
 
     // Install modules needed for this test. This could have been passed in as
     // either a single array argument or a variable number of string arguments.
diff --git a/modules/system/system.admin.inc b/modules/system/system.admin.inc
index b7e6fc9e70..f9244e7b7a 100644
--- a/modules/system/system.admin.inc
+++ b/modules/system/system.admin.inc
@@ -1275,7 +1275,7 @@ function system_modules_uninstall($form, $form_state = NULL) {
   // Only build the rest of the form if there are any modules available to
   // uninstall.
   if (!empty($disabled_modules)) {
-    $profile = drupal_get_profile();
+    $profiles = drupal_get_profiles();
     uasort($disabled_modules, 'system_sort_modules_by_info_name');
     $form['uninstall'] = array('#tree' => TRUE);
     foreach ($disabled_modules as $module) {
@@ -1292,7 +1292,7 @@ function system_modules_uninstall($form, $form_state = NULL) {
       // we can allow this module to be uninstalled. (The installation profile
       // is excluded from this list.)
       foreach (array_keys($module->required_by) as $dependent) {
-        if ($dependent != $profile && drupal_get_installed_schema_version($dependent) != SCHEMA_UNINSTALLED) {
+        if (!in_array($dependent, $profiles) && drupal_get_installed_schema_version($dependent) != SCHEMA_UNINSTALLED) {
           $dependent_name = isset($all_modules[$dependent]->info['name']) ? $all_modules[$dependent]->info['name'] : $dependent;
           $form['modules'][$module->name]['#required_by'][] = $dependent_name;
           $form['uninstall'][$module->name]['#disabled'] = TRUE;
diff --git a/modules/system/system.install b/modules/system/system.install
index 3bb07d955e..5fa36969dc 100644
--- a/modules/system/system.install
+++ b/modules/system/system.install
@@ -443,11 +443,11 @@ function system_requirements($phase) {
 
   // Display an error if a newly introduced dependency in a module is not resolved.
   if ($phase == 'update') {
-    $profile = drupal_get_profile();
+    $profiles = drupal_get_profiles();
     $files = system_rebuild_module_data();
     foreach ($files as $module => $file) {
       // Ignore disabled modules and installation profiles.
-      if (!$file->status || $module == $profile) {
+      if (!$file->status || in_array($module, $profiles)) {
         continue;
       }
       // Check the module's PHP version.
diff --git a/modules/system/system.module b/modules/system/system.module
index 4ce6b9b99d..b9f5fe8173 100644
--- a/modules/system/system.module
+++ b/modules/system/system.module
@@ -2371,15 +2371,18 @@ function _system_rebuild_module_data() {
   // Find modules
   $modules = drupal_system_listing('/^' . DRUPAL_PHP_FUNCTION_PATTERN . '\.module$/', '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';
+  // Include the active install profile(s) in modules that are loaded.
+  $profile_weight = 1000;
+  $profiles = drupal_get_profiles();
+  foreach ($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 = 1000;
+    // Install profile hooks are always executed last.
+    $modules[$profile]->weight = $profile_weight++;
+  }
 
   // Set defaults for module info.
   $defaults = array(
@@ -2429,7 +2432,7 @@ function _system_rebuild_module_data() {
 
     // Installation profiles are hidden by default, unless explicitly specified
     // otherwise in the .info file.
-    if ($key == $profile && !isset($modules[$key]->info['hidden'])) {
+    if (in_array($key, $profiles) && !isset($modules[$key]->info['hidden'])) {
       $modules[$key]->info['hidden'] = TRUE;
     }
 
@@ -2439,13 +2442,15 @@ function _system_rebuild_module_data() {
     drupal_alter('system_info', $modules[$key]->info, $modules[$key], $type);
   }
 
-  if (isset($modules[$profile])) {
-    // 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
-    // matches the default value used in install_profile_info().
-    if (!isset($modules[$profile]->info['distribution_name'])) {
-      $modules[$profile]->info['distribution_name'] = 'Drupal';
+  foreach ($profiles as $profile) {
+    if (isset($modules[$profile])) {
+      // 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 matches the default value used in install_profile_info().
+      if (!isset($modules[$profile]->info['distribution_name'])) {
+        $modules[$profile]->info['distribution_name'] = 'Drupal';
+      }
     }
   }