An extension guide assembly for use on a side of a drawer to guide movement of the drawer into and out of a furniture body includes a support rail to be attached to the furniture body, an extension rail to be attached to the drawer, and a central rail between the extension rail and the support rail. The central rail has a U-shaped transverse profile opening downwardly, and carriages are positioned within the profile of the central rail and support rolling bodies transferring the load of the drawer from the central rail to the support rail. Guide members or runners are disposed on top of the central rail between the central rail and the extension rail. The extension rail has a downwardly open U-shaped transverse cross section including an upper horizontal leg above the guide members, lateral vertical legs extending downwardly from opposite sides of the upper horizontal leg along respective sides of the guide members, and a lower horizontal leg extending from one of the vertical legs to a position beneath each guide member. Thereby the extension rail and drawer are prevented from being lifted from the guide members and the central rail.