Index: wp-includes/js/media-editor.js
===================================================================
--- wp-includes/js/media-editor.js	(revision 23074)
+++ wp-includes/js/media-editor.js	(working copy)
@@ -554,7 +554,8 @@
 				props = wp.media.string.props( props, attachment );
 
 				options = {
-					id: attachment.id
+					id:           attachment.id,
+					post_content: attachment.description
 				};
 
 				if ( props.linkUrl )
Index: wp-includes/js/media-views.js
===================================================================
--- wp-includes/js/media-views.js	(revision 23076)
+++ wp-includes/js/media-views.js	(working copy)
@@ -2829,7 +2829,8 @@
 					width:         '',
 					height:        '',
 					compat:        false,
-					alt:           ''
+					alt:           '',
+					description:   '',
 				});
 
 			options.buttons  = this.buttons;
Index: wp-includes/media.php
===================================================================
--- wp-includes/media.php	(revision 23076)
+++ wp-includes/media.php	(working copy)
@@ -1749,6 +1749,10 @@
 				<# } #>/>
 			</label>
 		<# } #>
+			<label class="setting" data-setting="description">
+				<span><?php _e('Description'); ?></span>
+				<textarea {{ maybeReadOnly }}>{{ data.description }}</textarea>
+			</label>
 	</script>
 
 	<script type="text/html" id="tmpl-media-selection">
Index: wp-admin/includes/ajax-actions.php
===================================================================
--- wp-admin/includes/ajax-actions.php	(revision 23074)
+++ wp-admin/includes/ajax-actions.php	(working copy)
@@ -1884,6 +1884,9 @@
 	if ( isset( $changes['caption'] ) )
 		$post['post_excerpt'] = $changes['caption'];
 
+	if ( isset( $changes['description'] ) )
+		$post['post_content'] = $changes['description'];
+
 	if ( isset( $changes['alt'] ) ) {
 		$alt = get_post_meta( $id, '_wp_attachment_image_alt', true );
 		$new_alt = stripslashes( $changes['alt'] );
Index: wp-admin/includes/meta-boxes.php
===================================================================
--- wp-admin/includes/meta-boxes.php	(revision 23074)
+++ wp-admin/includes/meta-boxes.php	(working copy)
@@ -313,7 +313,7 @@
 	);
 ?>
 <p>
-	<label class="screen-reader-text" for="content"><strong><?php _e( 'Attachment Page Content' ); ?></strong></label>
+	<label class="screen-reader-text" for="content"><strong><?php _e( 'Description' ); ?></strong></label>
 	<?php wp_editor( $post->post_content, 'attachment_content', $editor_args ); ?>
 </p>
 <?php
Index: wp-admin/includes/media.php
===================================================================
--- wp-admin/includes/media.php	(revision 23074)
+++ wp-admin/includes/media.php	(working copy)
@@ -1329,12 +1329,9 @@
 	$form_fields = apply_filters( 'attachment_fields_to_edit', $form_fields, $post );
 
 	unset( $form_fields['image-size'], $form_fields['align'], $form_fields['image_alt'],
-		$form_fields['post_title'], $form_fields['post_excerpt'],
+		$form_fields['post_title'], $form_fields['post_excerpt'], $form_fields['post_content'],
 		$form_fields['url'], $form_fields['menu_order'], $form_fields['image_url'] );
 
-	if ( ! $args['description'] )
-		unset( $form_fields['post_content'] );
-
 	$media_meta = apply_filters( 'media_meta', '', $post );
 
 	$defaults = array(
Index: wp-admin/edit-form-advanced.php
===================================================================
--- wp-admin/edit-form-advanced.php	(revision 23074)
+++ wp-admin/edit-form-advanced.php	(working copy)
@@ -107,7 +107,7 @@
 	wp_enqueue_script( 'image-edit' );
 	wp_enqueue_style( 'imgareaselect' );
 	add_meta_box( 'submitdiv', __('Save'), 'attachment_submit_meta_box', null, 'side', 'core' );
-	add_meta_box( 'attachmentdata', __('Attachment Page Content'), 'attachment_content_meta_box', null, 'normal', 'core' );
+	add_meta_box( 'attachmentdata', __('Description'), 'attachment_content_meta_box', null, 'normal', 'core' );
 	add_action( 'edit_form_after_title', 'edit_form_image_editor' );
 } else {
 	add_meta_box( 'submitdiv', __( 'Publish' ), 'post_submit_meta_box', null, 'side', 'core' );