Abstract: This invention provides an automated single pass dialysate supply apparatus and a method for conducting hemodialysis treatments when the apparatus is used. The apparatus is of the closed circuit type and provides a pair of cylinders, each equipped with a hydraulically driven diaphragm, which supply fresh dialysate to and remove spent dialysate from an artificial kidney on an alternating time basis; the improvement resides in the means which sense the difference in time of arrival of the end of stroke of each diaphragm and automatically counteract these differences to either maintain or restore synchronization of the instant of end of stroke of each diaphragm in each half cycle of operation.The hemodialysis treatment method permits operator presetting of the desired ultrafiltrate removal rate and insures maintenance of that preset rate throughout the hemodialysis treatment period.