Abstract: Sheet stacking apparatus having a variable speed conveyor on which sheets are carried in partially overlapped or "shingled" relation and deposited onto a second variable speed conveyor disposed in end-to-end relation to the first conveyor for receiving sheets therefrom and projecting onto a vertically movable stacking conveyor which lowers automatically as the stack builds up. Feed stop mechanism is disposed to stop and release selectively the flow of sheets from the first conveyor onto the second conveyor in response to the "full stack" position of the stacking conveyor. Control means is provided for changing the speed of the two conveyors in sequential relationship to the actuation of the stop mechanism whereby the speed of the first conveyor is substantially reduced, while the speed of the second conveyor is substantially increased to clear the latter preparatory to discharge of the stacking conveyor.