Abstract: An extendible conveyor apparatus includes a first end, a second end, and an adjustable-length bed of rollers extending in between them. A sliding frame (or extension) mounted moveably on a support structure supports a fixed number of the rollers, while a moveable string of rollers connected to a second end of the frame feeds additional rollers into and out of position between the second end of the conveyor apparatus and the frame according to frame movement between retracted and extended positions of the frame. In one embodiment, the bed of rollers includes at least some motor-driven rollers (MDRs) and the string of rollers withdraws to a position below the bed using an extend/retract drive mechanism having a drive chain disposed in a loop, the frame being connected to an upper side of the loop for frame-moving purposes and the string of rollers being connected to a lower side of the loop for string withdrawal purposes.