Abstract: A discharge flow control rate valve for a multiple cylinder type reciprocating pump has a flow rate control valve associated with two cylinders of the pump. The flow control valve has a bypass passage connecting the suction side of the pump with a stepped cylinder chamber provided in the body member of the control valve. A needle valve fitted with a separate valving element is reciprocably disposed in the stepped cylinder chamber and operates to return a part of the fluid in the first cylinder or in the first and second cylinders to the suction side of the pump as a function of the intrusion distance of the valve into the cylinder chamber so as to modify the overall discharge flow rate of the pump.