Bag top registration apparatus includes infeed mechanism that feeds bags, which may be of different lengths, from a magazine to positioner assemblies which have back lights and bag clamps that are operable for moving the bags, if necessary, to have their bag top edges over the back lights at registration positions and pick-up mechanism for transferring the bags at registration positions to a conveyor assembly with their top edges at the same elevation. Cameras take images of the bags on the positioner assemblies extending in part over the back lights. The programmable logic controller in comparing the images with the parameters imparted by a human machine interface controls the operation of the clamps to move the bags to the registration positions and the mechanism for removing the bags from the magazine, the clamps, the pick-up mechanism and the conveyor assembly.