If you are considering the upgrade to Rails 3.1.x and you wish to include the JQuery-UI in your web application follow these simple steps: Load jquery-ui in your app/assets/javascripts/application.js //= require jquery //= require jquery_ujs //= require jquery-ui //= require_tree . Pick and download a nice theme from: JQuery-UI themes site Copy jquery-ui-1.8.16.custom.css(version number could differ) [...]