A hydraulic control device is incorporated in a hydraulic control system for a mine roof support assembly. The hydraulic control system includes a plurality of hydraulic control valves which are controlled by the hydraulic control device. The hydraulic control device is constituted by a longitudinal slide valve having a slide member longitudinally reciprocable in a slide valve housing. A rotary drive is provided for moving the slide member within the slide valve housing. The slide member is provided with two axial bores each of which opens into a respective pair of axially-spaced radial bores which terminate at the peripheral surface of the slide member. A first radial bore of each axial bore opens into a respective annular groove formed in the slide valve housing. The second radial bore of each axial bore is connected to a respective group of control ports provided on the slide valve housing. The control ports of each group are axially spaced, and are connected to the hydraulic control valves by respective hydraulic control lines.