A suction control valve for a closed system suction catheter has a housing 31 with an inlet bore 34 and an outlet bore 38 inclined at an angle to the inlet bore and opening into the bore via an aperture 4. A valve member 50 comprises a rod member 52 and a manually actuable plate 62 extending longitudinally in an external channel 47 along the housing 31 between two walls 48 and 49. The rod member 50 supports a resilient sleeve 54 and its forward end 57 is urged, by a spring 64, to engage a tapered seal 40 within the housing forwardly of the aperture 4, thereby blocking flow through the valve. The valve is opened by sliding the plate 62 rearwardly so that the valve member 59 moves rearwardly of the aperture 4. A locking cap 70 can be twisted to prevent movement of the valve member 50 from its closed position.
