Abstract: A source of power rotates a drive shaft upon which a pair of rollers are mounted. The rollers rotate in a recess and collapse an undialysed blood carrying tube against a wall thus causing a pumping action. When used with a single needle dialysis system, an occluding pin assembly intermittently clamps off the dialysed blood carrying tube as said source of power is interrupted in rotation thus permitting the device to be used with a conventional single needle assembly. By rotating a cylindrical member upon the upper end of the drive shaft, the rollers can be retracted from adjacent the wall against which the undialysed blood carrying tube rests thus facilitating the engagement and disengagement of the undialysed blood carrying tube with the device. Inasmuch as the wall thickness of such tubes often varies, between tubing produced by different manufacturers, means are provided to adjust the spatial relationship of the pump rollers with the wall against which the tube is pressed during the pumping action.