Abstract: A continuous control valve is disclosed which comprises a casing having a cylindrical cavity therein with two pairs of ports extending therethrough. Each port has a preferably square opening communicating with the cavity. A cylindrical valve slide is movable both axially and rotatably in the casing cavity. The valve slide includes a pair of rectangular cross section grooves which have control edges movable with respect to limiting edges of the port openings to vary the cross sectional area of the port openings opening into the groove. Each groove is shallow in the vicinity of inlet and outlet port openings and deeper in the vicinity of additional port openings in the casing. The cylindrical valve is movable either axially or rotationally in a controlled direction to vary the cross-sectional area of the passages and also movable into a selected position to establish a selected overlap between the control edges of the valve slide and the limiting edges of the port openings.