diff --git a/includes/common.inc b/includes/common.inc
index f04ce4a9483..4e4a0e3563b 100644
--- a/includes/common.inc
+++ b/includes/common.inc
@@ -3826,7 +3826,7 @@ function drupal_set_page_content($content = NULL) {
  *   A string or array representing the content of a page. The array consists of
  *   the following keys:
  *   - #type: Value is always 'page'. This pushes the theming through page.tpl.php (required).
- *   - #show_blocks: A marker which suppresses left/right regions if FALSE (optional).
+ *   - #show_blocks: A marker which suppresses sidebar regions if FALSE (optional).
  *   - #show_messages: Suppress drupal_get_message() items. Used by Batch API (optional).
  *
  * @see hook_page_alter()
@@ -3841,7 +3841,7 @@ function drupal_render_page($page) {
     $page = element_info('page');
   }
   // Modules alter the $page as needed. Blocks are populated into regions like
-  // 'left', 'footer', etc.
+  // 'sidebar_first', 'footer', etc.
   drupal_alter('page', $page);
 
   return drupal_render($page);
diff --git a/install.php b/install.php
index 8df7a0e94a9..48cc2126d20 100644
--- a/install.php
+++ b/install.php
@@ -674,7 +674,7 @@ function install_display_output($output, $install_state) {
     // Let the theming function know when every step of the installation has
     // been completed.
     $active_task = $install_state['installation_finished'] ? NULL : $install_state['active_task'];
-    drupal_add_region_content('left', theme_task_list(install_tasks_to_display($install_state), $active_task));
+    drupal_add_region_content('sidebar_first', theme_task_list(install_tasks_to_display($install_state), $active_task));
   }
   print theme($install_state['database_tables_exist'] ? 'maintenance_page' : 'install_page', $output);
   exit;
diff --git a/modules/block/block.api.php b/modules/block/block.api.php
index c1f5d6145b2..96c04e06e51 100644
--- a/modules/block/block.api.php
+++ b/modules/block/block.api.php
@@ -57,7 +57,7 @@ function hook_block_list() {
     'info' => t('An exciting block provided by Mymodule.'),
     'weight' => 0,
     'status' => 1,
-    'region' => 'left',
+    'region' => 'sidebar_first',
     // BLOCK_CACHE_PER_ROLE will be assumed for block 0.
   );
 
diff --git a/modules/system/system.api.php b/modules/system/system.api.php
index 37d37ea1559..cbfc78dd142 100644
--- a/modules/system/system.api.php
+++ b/modules/system/system.api.php
@@ -304,9 +304,9 @@ function hook_css_alter(&$css) {
  * The $page array contains top level elements for each block region:
  * @code
  *   $page['header']
- *   $page['left']
+ *   $page['sidebar_first']
  *   $page['content']
- *   $page['right']
+ *   $page['sidebar_second']
  *   $page['footer']
  * @endcode
  *
@@ -330,8 +330,8 @@ function hook_css_alter(&$css) {
  *
  * Blocks may be referenced by their module/delta pair within a region:
  * @code
- *   // The login block in the left sidebar region.
- *   $page['left']['user-login']['#block'];
+ *   // The login block in the first sidebar region.
+ *   $page['sidebar_first']['user-login']['#block'];
  * @endcode
  *
  * @param $page
diff --git a/profiles/expert/expert.profile b/profiles/expert/expert.profile
index aebb6062eaf..dd8a5e19482 100644
--- a/profiles/expert/expert.profile
+++ b/profiles/expert/expert.profile
@@ -40,7 +40,7 @@ function expert_profile_site_setup(&$install_state) {
       'theme' => 'garland',
       'status' => 1,
       'weight' => 0,
-      'region' => 'left',
+      'region' => 'sidebar_first',
       'pages' => '',
       'cache' => -1,
     ),
@@ -50,7 +50,7 @@ function expert_profile_site_setup(&$install_state) {
       'theme' => 'garland',
       'status' => 1,
       'weight' => 0,
-      'region' => 'left',
+      'region' => 'sidebar_first',
       'pages' => '',
       'cache' => -1,
     ),
@@ -60,7 +60,7 @@ function expert_profile_site_setup(&$install_state) {
       'theme' => 'garland',
       'status' => 1,
       'weight' => 1,
-      'region' => 'left',
+      'region' => 'sidebar_first',
       'pages' => '',
       'cache' => -1,
     ),
diff --git a/update.php b/update.php
index f37b9c2b37c..d00b55311ac 100644
--- a/update.php
+++ b/update.php
@@ -240,7 +240,7 @@ function update_task_list($active = NULL) {
     'finished' => 'Review log',
   );
 
-  drupal_add_region_content('left', theme('task_list', $tasks, $active));
+  drupal_add_region_content('sidebar_first', theme('task_list', $tasks, $active));
 }
 
 /**