Abstract: Multiple copies of sheets produced by a duplicator, xerographic copier or the like are sorted onto trays. The trays are arranged in a stack and are moved upwardly and downwardly to enable different sheets to be sorted onto the trays on each upward pass and downward pass of the stack. A carriage retains the stack and moves upwardly and downwardly with the stack as individual trays are engaged and translated around a region where adjacent trays are spread apart to register the trays successively at a position where individual sheets are received thereon. Bidirectional movement of the entire stack of trays with a mechanism which raises or lowers a single tray provides a sorter of compact size which is simple, reliable and low in cost and which operates without generating excessive noise.