diff --git a/core/authorize.php b/core/authorize.php
index fe39394..5797188 100644
--- a/core/authorize.php
+++ b/core/authorize.php
@@ -118,7 +118,11 @@ function authorize_access_allowed() {
       drupal_set_message($results['page_message']['message'], $results['page_message']['type']);
     }
 
-    $output = theme('authorize_report', array('messages' => $results['messages']));
+    $authorize_report = array(
+      '#theme' => 'authorize_report',
+      '#messages' => $results['messages'],
+    );
+    $output = drupal_render($authorize_report);
 
     $links = array();
     if (is_array($results['tasks'])) {
@@ -131,7 +135,12 @@ function authorize_access_allowed() {
       ));
     }
 
-    $output .= theme('item_list', array('items' => $links, 'title' => t('Next steps')));
+    $item_list = array(
+      '#theme' => 'item_list',
+      '#items' => $links,
+      '#title' => t('Next steps'),
+    );
+    $output .= drupal_render($item_list);
   }
   // If a batch is running, let it run.
   elseif (isset($_GET['batch'])) {
@@ -156,5 +165,10 @@ function authorize_access_allowed() {
 
 if (!empty($output)) {
   drupal_add_http_header('Content-Type', 'text/html; charset=utf-8');
-  print theme('maintenance_page', array('content' => $output, 'show_messages' => $show_messages));
+  $maintenance_page = array(
+    '#theme' => 'maintenance_page',
+    '#content' => $output,
+    '#show_messages' => $show_messages,
+  );
+  print drupal_render($maintenance_page);
 }
diff --git a/core/includes/ajax.inc b/core/includes/ajax.inc
index 1bced44..4193e31 100644
--- a/core/includes/ajax.inc
+++ b/core/includes/ajax.inc
@@ -398,7 +398,8 @@ function ajax_prepare_response($page_callback_result) {
     $commands[] = ajax_command_insert(NULL, $html);
     // Add the status messages inside the new content's wrapper element, so that
     // on subsequent Ajax requests, it is treated as old content.
-    $commands[] = ajax_command_prepend(NULL, theme('status_messages'));
+    $status_messages = array('#theme' => 'status_messages');
+    $commands[] = ajax_command_prepend(NULL, drupal_render($status_messages));
   }
 
   return $commands;
diff --git a/core/includes/batch.inc b/core/includes/batch.inc
index 569ce58..b70d2d5 100644
--- a/core/includes/batch.inc
+++ b/core/includes/batch.inc
@@ -119,7 +119,12 @@ function _batch_progress_page() {
     // the error message.
     ob_start();
     $fallback = $current_set['error_message'] . '<br />' . $batch['error_message'];
-    $fallback = theme('maintenance_page', array('content' => $fallback, 'show_messages' => FALSE));
+    $maintenance_page = array(
+      '#theme' => 'maintenance_page',
+      '#content' => $fallback,
+      '#show_messages' => FALSE,
+    );
+    $fallback = drupal_render($maintenance_page);
 
     // We strip the end of the page using a marker in the template, so any
     // additional HTML output by PHP shows up inside the page rather than below
@@ -167,7 +172,13 @@ function _batch_progress_page() {
   drupal_add_js($js_setting, 'setting');
   drupal_add_library('system', 'drupal.batch');
 
-  return theme('progress_bar', array('percent' => $percentage, 'message' => $message, 'label' => $label));
+  $progress_bar = array(
+    '#theme' => 'progress_bar',
+    '#percent' => $percentage,
+    '#message' => $message,
+    '#label' => $label,
+  );
+  return drupal_render($progress_bar);
 }
 
 /**
diff --git a/core/includes/common.inc b/core/includes/common.inc
index 842136e..8f88985 100644
--- a/core/includes/common.inc
+++ b/core/includes/common.inc
@@ -391,7 +391,12 @@ function drupal_add_feed($url = NULL, $title = '') {
   $stored_feed_links = &drupal_static(__FUNCTION__, array());
 
   if (isset($url)) {
-    $stored_feed_links[$url] = theme('feed_icon', array('url' => $url, 'title' => $title));
+    $feed_icon = array(
+      '#theme' => 'feed_icon',
+      '#url' => $url,
+      '#title' => $title,
+    );
+    $stored_feed_links[$url] = drupal_render($feed_icon);
 
     drupal_add_html_head_link(array(
       'rel' => 'alternate',
diff --git a/core/includes/errors.inc b/core/includes/errors.inc
index 3fe23b7..a8257f2 100644
--- a/core/includes/errors.inc
+++ b/core/includes/errors.inc
@@ -276,7 +276,11 @@ function _drupal_log_error($error, $fatal = FALSE) {
       // We fallback to a maintenance page at this point, because the page generation
       // itself can generate errors.
       // Should not translate the string to avoid errors producing more errors.
-      $output = theme('maintenance_page', array('content' => 'The website has encountered an error. Please try again later.'));
+      $maintenance_page = array(
+        '#theme' => 'maintenance_page',
+        '#content' => 'The website has encountered an error. Please try again later.',
+      );
+      $output = drupal_render($maintenance_page);
 
       $response = new Response($output, 500);
       if ($fatal) {
diff --git a/core/includes/form.inc b/core/includes/form.inc
index d63596e..779457e 100644
--- a/core/includes/form.inc
+++ b/core/includes/form.inc
@@ -3523,7 +3523,14 @@ function theme_tableselect($variables) {
       array_unshift($header, '');
     }
   }
-  return theme('table', array('header' => $header, 'rows' => $rows, 'empty' => $element['#empty'], 'attributes' => $element['#attributes']));
+  $table = array(
+    '#theme' => 'table',
+    '#header' => $header,
+    '#rows' => $rows,
+    '#empty' => $element['#empty'],
+    '#attributes' => $element['#attributes'],
+  );
+  return drupal_render($table);
 }
 
 /**
@@ -4712,17 +4719,23 @@ function theme_form_element($variables) {
   }
   $prefix = isset($element['#field_prefix']) ? '<span class="field-prefix">' . $element['#field_prefix'] . '</span> ' : '';
   $suffix = isset($element['#field_suffix']) ? ' <span class="field-suffix">' . $element['#field_suffix'] . '</span>' : '';
+  $form_element_label = array('#theme' => 'form_element_label');
+  foreach (array('#title', '#title_display', '#required', '#id') as $key) {
+    if (isset($element[$key]) || array_key_exists($key, $element)) {
+      $form_element_label[$key] = $element[$key];
+    }
+  }
 
   switch ($element['#title_display']) {
     case 'before':
     case 'invisible':
-      $output .= ' ' . theme('form_element_label', $variables);
+      $output .= ' ' . drupal_render($form_element_label);
       $output .= ' ' . $prefix . $element['#children'] . $suffix . "\n";
       break;
 
     case 'after':
       $output .= ' ' . $prefix . $element['#children'] . $suffix;
-      $output .= ' ' . theme('form_element_label', $variables) . "\n";
+      $output .= ' ' . drupal_render($form_element_label) . "\n";
       break;
 
     case 'none':
@@ -4794,7 +4807,8 @@ function theme_form_element_label($variables) {
   }
 
   // If the element is required, a required marker is appended to the label.
-  $required = !empty($element['#required']) ? theme('form_required_marker', array('element' => $element)) : '';
+  $form_required_marker = array('#theme' => 'form_required_marker') + $element;
+  $required = !empty($element['#required']) ? drupal_render($form_required_marker) : '';
 
   $title = filter_xss_admin($element['#title']);
 
diff --git a/core/includes/install.core.inc b/core/includes/install.core.inc
index 8789366..8b17ed4 100644
--- a/core/includes/install.core.inc
+++ b/core/includes/install.core.inc
@@ -949,9 +949,19 @@ function install_display_output($output, $install_state) {
     // Let the theming function know when every step of the installation has
     // been completed.
     $active_task = $install_state['installation_finished'] ? NULL : $install_state['active_task'];
-    drupal_add_region_content('sidebar_first', theme('task_list', array('items' => install_tasks_to_display($install_state), 'active' => $active_task, 'variant' => 'install')));
+    $task_list = array(
+      '#theme' => 'task_list',
+      '#items' => install_tasks_to_display($install_state),
+      '#active' => $active_task,
+      '#variant' => 'install',
+    );
+    drupal_add_region_content('sidebar_first', drupal_render($task_list));
   }
-  print theme('install_page', array('content' => $output));
+  $install_page = array(
+    '#theme' => 'install_page',
+    '#content' => $output,
+  );
+  print drupal_render($install_page);
   exit;
 }
 
@@ -2352,9 +2362,13 @@ function install_display_requirements($install_state, $requirements) {
   if ($severity == REQUIREMENT_ERROR || ($severity == REQUIREMENT_WARNING && empty($install_state['parameters']['continue']))) {
     if ($install_state['interactive']) {
       drupal_set_title(t('Requirements problem'));
-      $status_report = theme('status_report', array('requirements' => $requirements));
-      $status_report .= t('Check the messages and <a href="!url">try again</a>.', array('!url' => check_url(drupal_requirements_url($severity))));
-      return $status_report;
+      $status_report = array(
+        '#theme' => 'status_report',
+        '#requirements' => $requirements,
+      );
+      $output = drupal_render($status_report);
+      $output .= t('Check the messages and <a href="!url">try again</a>.', array('!url' => check_url(drupal_requirements_url($severity))));
+      return $output;
     }
     else {
       // Throw an exception showing any unmet requirements.
diff --git a/core/includes/tablesort.inc b/core/includes/tablesort.inc
index c42b1f4..a9bbc56 100644
--- a/core/includes/tablesort.inc
+++ b/core/includes/tablesort.inc
@@ -49,7 +49,11 @@ function tablesort_header($cell, $header, $ts) {
       $cell['aria-sort'] = ($ts['sort'] == 'asc') ? 'ascending' : 'descending';
       $ts['sort'] = (($ts['sort'] == 'asc') ? 'desc' : 'asc');
       $cell['class'][] = 'active';
-      $image = theme('tablesort_indicator', array('style' => $ts['sort']));
+      $tablesort_indicator = array(
+        '#theme' => 'tablesort_indicator',
+        '#style' => $ts['sort'],
+      );
+      $image = drupal_render($tablesort_indicator);
     }
     else {
       // If the user clicks a different header, we want to sort ascending initially.
diff --git a/core/includes/theme.inc b/core/includes/theme.inc
index 5296b08..58fc418 100644
--- a/core/includes/theme.inc
+++ b/core/includes/theme.inc
@@ -2304,7 +2304,14 @@ function theme_item_list($variables) {
  */
 function theme_feed_icon($variables) {
   $text = t('Subscribe to !feed-title', array('!feed-title' => $variables['title']));
-  if ($image = theme('image', array('uri' => 'core/misc/feed.png', 'width' => 16, 'height' => 16, 'alt' => $text))) {
+  $build = array(
+    '#theme' => 'image',
+    '#uri' => 'core/misc/feed.png',
+    '#width' => 16,
+    '#height' => 16,
+    '#alt' => $text,
+  );
+  if ($image = drupal_render($build)) {
     return l($image, $variables['url'], array('html' => TRUE, 'attributes' => array('class' => array('feed-icon'), 'title' => $text)));
   }
 }
@@ -2873,6 +2880,7 @@ function template_preprocess_maintenance_page(&$variables) {
   );
   drupal_render($default_css);
 
+  $status_messages = array('#theme' => 'status_messages');
   $variables['head_title_array']  = $head_title;
   $variables['head_title']        = implode(' | ', $head_title);
   $variables['base_path']         = base_path();
@@ -2883,7 +2891,7 @@ function template_preprocess_maintenance_page(&$variables) {
   $variables['language']          = $language_interface;
   $variables['language']->dir     = $language_interface->direction ? 'rtl' : 'ltr';
   $variables['logo']              = theme_get_setting('logo.url');
-  $variables['messages']          = $variables['show_messages'] ? theme('status_messages') : '';
+  $variables['messages']          = $variables['show_messages'] ? drupal_render($status_messages) : '';
   $variables['main_menu']         = array();
   $variables['secondary_menu']    = array();
   $variables['site_name']         = (theme_get_setting('features.name') ? check_plain($site_name) : '');
diff --git a/core/includes/theme.maintenance.inc b/core/includes/theme.maintenance.inc
index 5c35ac3..61e5ee5 100644
--- a/core/includes/theme.maintenance.inc
+++ b/core/includes/theme.maintenance.inc
@@ -170,9 +170,19 @@ function theme_authorize_report($variables) {
         if ($number === '#abort') {
           continue;
         }
-        $items[] = theme('authorize_message', array('message' => $log_message['message'], 'success' => $log_message['success']));
+        $authorize_message = array(
+          '#theme' => 'authorize_message',
+          '#message' => $log_message['message'],
+          '#success' => $log_message['success'],
+        );
+        $items[] = drupal_render($authorize_message);
       }
-      $output .= theme('item_list',  array('items' => $items, 'title' => $heading));
+      $item_list = array(
+        '#theme' => 'item_list',
+        '#items' => $items,
+        '#title' => $heading,
+      );
+      $output .= drupal_render($item_list);
     }
     $output .= '</div>';
   }