This chapter examines both the therapeutic aspects of functional electrical stimulation (FES) as well as the direct functional applications as it is applied to individuals with neurologic injury. FES systems typically consist of three major components. First, there is a control mechanism. Second, there is an electronic stimulator, which may be external or implanted. Third, there are electrodes that allow for interface between the stimulator and the nervous system. There are several important parameters that can be adjusted during FES application, including pulse waveform, amplitude, duration, frequency, charge, and modulations. The option of interrupted pulses is mandatory in most neurorehabilitation clinical applications. Functional uses for FES after spinal cord injury (SCI) include applications in standing, walking, hand grasp, bladder and bowel function, respiratory assist, and electroejaculation. Several neuroprosthetic devices have gone through regulatory review and have reached the clinical world.