A micropower bipolar implantable stimulator has been developed and tested for long-term (four weeks-six months) use in experiments involving the stimulation of denervated skeletal muscle. Implantable stimulators are typically operated from a single lithium battery at 3 V. After the first week of denervation, stimulation of denervated muscles of rats requires voltages in the range of 6-12 V. The stimulator described can deliver voltages up to 15 V, with variable pulsewidth, frequency and duty cycle. All stimulation parameters are set prior to implantation by selection of appropriate resistors and capacitors. Each primary failure mode for implantable stimulators is addressed. Long-term reliability rates in excess of 95% are achievable if the construction details are followed closely. Methods for battery power management, circuit component selection, electrode construction and encapsulation are described in detail. This device is not intended for use in humans.