Abstract: A screw compressor including a coacting male and female rotor with respect to which a slide valve is operable to control the discharge of the compressor and also regulate the pressure of the fluid pumped or compressed thereby, the improvement comprising a limited number of different embodiments of anti-friction constructions for supporting the slide valve within the cylindrical bore provided therefor in the housing within which the male and female rotors operate, thereby minimizing the wear upon the slide valve within the bore therefor and minimizing the force required to move the slide valve.