This paper describes an improved Functional Microstimulation (FES) system for restoring paralyzed extremities in spinal cord injury patients. The system, which creates electrical stimulus patterns for individual muscles, was developed with an IBM PC. In this improved, portable FES system — which uses a V40 microprocessor, a D/A converter, and a 32-channel multiplexer — muscle fatigue can be eased by the selection of a stimulus frequency appropriate for a particular muscle. Driving software for the system is programmed with an assembler and C language.