diff --git a/bulk-user-management.php b/bulk-user-management.php
index 27d4853..048307a 100644
--- a/bulk-user-management.php
+++ b/bulk-user-management.php
@@ -297,6 +297,10 @@ public function handle_promote_users_form() {
 	public function promote_users($blogids = array(), $userids = array(), $role) {
 		foreach ( $userids as $id ) {
 			foreach ( $blogids as $blogid ) {
+				// Is the current user already a member of the blog with the given `$role`? If so, continue.
+				if ( count ( get_users( array( 'blog_id' => $blogid, 'role' => $role, 'include' => array ( $id ) ) ) ) > 0 ) {
+					continue;
+				}
 				add_user_to_blog( $blogid, $id, $role );
 			}
 		}
@@ -358,6 +362,10 @@ public function handle_remove_users_form() {
 	public function remove_users($blogids = array(), $userids = array()) {
 		foreach ( $userids as $userid ) {
 			foreach ( $blogids as $blogid ) {
+				// Is the current user already not a member of the blog? If so, continue.
+				if ( count ( get_users( array( 'blog_id' => $blogid, 'include' => array ( $userid ) ) ) ) == 0 ) {
+					continue;
+				}
 				remove_user_from_blog( $userid, $blogid );
 			}
 		}
diff --git a/includes/class-bulk-user-table.php b/includes/class-bulk-user-table.php
index e92f9d0..cbc38b2 100644
--- a/includes/class-bulk-user-table.php
+++ b/includes/class-bulk-user-table.php
@@ -223,7 +223,10 @@ function inline_edit() {
 		</div></fieldset>
 
 		<fieldset class="inline-edit-col-middle"><div class="inline-edit-col">
-			<span class="title inline-edit-categories-label"><?php _e( 'Sites', 'bulk-user-management' ) ?></span>
+			<span class="title inline-edit-categories-label">
+				<?php _e( 'Sites', 'bulk-user-management' ) ?>
+				&nbsp;&nbsp;<input class="select-all-sites" type="checkbox" name="select-all-sites" value="1" /><?php _e( 'Select All', 'bulk-user-management' ) ?>
+			</span>
 
 			<ul class="cat-checklist site-checklist">
 				<?php foreach ( $this->get_blog_ids( 'promote_users' ) as $id ): ?>
@@ -278,7 +281,10 @@ function bulk_remove() {
 		</div></fieldset>
 
 		<fieldset class="inline-edit-col-right-wide"><div class="inline-edit-col">
-			<span class="title inline-edit-categories-label"><?php _e( 'Sites', 'bulk-user-management' ) ?></span>
+			<span class="title inline-edit-categories-label">
+				<?php _e( 'Sites', 'bulk-user-management' ) ?>
+				&nbsp;&nbsp;<input class="select-all-sites" type="checkbox" name="select-all-sites" value="1" /><?php _e( 'Select All', 'bulk-user-management' ) ?>
+			</span>
 
 			<ul class="cat-checklist site-checklist">
 				<?php foreach ( $this->get_blog_ids( 'remove_users' ) as $id ): ?>
diff --git a/js/bulk-user-management-inline-edit.js b/js/bulk-user-management-inline-edit.js
index 27842cb..cf88eef 100644
--- a/js/bulk-user-management-inline-edit.js
+++ b/js/bulk-user-management-inline-edit.js
@@ -150,7 +150,17 @@ inlineEditUser = {
 	}
 };
 
-$(document).ready(function(){inlineEditUser.init();});
+$(document).ready(function(){
+	inlineEditUser.init();
+	$('.select-all-sites').on('click', function() {
+		if($(this).prop('checked')) {
+			$(this).parents('tr.bulk-edit-row').find('.site-checklist input').prop('checked', true);
+		}
+		else {
+			$(this).parents('tr.bulk-edit-row').find('.site-checklist input').prop('checked', false);
+		}
+	});
+});
 })(jQuery);
 
 function getParameterByName(name, url) {