The objective of this project is to develop an implantable stimulator system for electrical excitation of paralyzed skeletal muscle. This system will be utilized by high level (C5 and C6) spinal cord injury patients to provide controlled grasp and release in the hand. In this application, functional neuromuscular stimulation has previously been demonstrated to be effective by employing chronically indwelling percutaneous electrodes. Through the use of the implantable system, we expect that the ease of use of the system and its reliability will be improved, leading to greater independence for the quadriplegic patient. The objective of development of the implantable system will be met by: 1. Development of circuitry using a high density of integration to perform the stimulation function; 2. Development of techniques for encapsulation of the stimulator in a hermetic package suitable for extended periods of implantation (greater than 5 years); 3. Development of stimulation electrodes and lead wire interconnections which are suitable for use with the implantable stimulator; 4. Development of a programmable control transmitter which is worn externally by the subject and regulates the output of the implant stimulator in response to the control signals generated by the subject; 5. Evaluation of the entire system and individual subsystems (eg. electrodes, packaging) in vitro and in vivo, and modification of the design where necessary. The principal application of this study is the upper extremity in the quadriplegic subject. However, the technology being developed in this project is expected to be directly applicable to other neurological deficits, such as stroke and cerebral palsy, thus enabling researchers and clinicians to have a powerful new technique more available for rehabilitation of motor function.