Functional electrical stimulation (FES) has developed over the last 35 years to become a scientifically, technologically and clinically recognized field of interest in clinical medicine. FES has been applied to locomotion, grasping, ventilation, incontinence, and decubitus healing. However, all of these achievements illustrate the initial applications of FES; its true potential has not yet been realized. Recently, FES systems, which are miniaturized stimulation devices, have been utilized in the clinical setting. However, because the stimulating electrodes of the current FES devices are percutaneous electrodes, which are susceptible to wire breakage, and skin infection an implantable FES stimulating electrode has been introduced in the U.S. and Japan. In the present study, an external power supply method using radio frequency (RF) coupling and data transmission was developed for the control of the implantable FES device. In addition, we review the current understanding of FES devices and their application in clinical medicine.