This paper describes a servo-controlled roller pump system that can be applied to a variety of experimental situations that require either flow or pressure control. The roller pump employs a special race design that nearly eliminates the outflow pulsations inherent in conventional roller pumps. This pump simplifies servo-system design because the outflow rate is related to rotor speed by a fixed constant throughout a pump cycle. The system can control either speed or, with an appropriate feedback signal from an external transducer and preamplifier, the pressure on the output side of the pump. The time constant of the step response under speed control is less than 0.01 s, whereas that for pressure control is less than 0.2 s. System operation in the speed mode is independent of pump loading. In the pressure control mode, system operation is optimized for particular loading conditions by a single gain control. The pump can control pressure in loads ranging from a blind-ended tube through loads accepting up to 1 l/min.