Both pulsatile (AC) and continuous (DC) electrical fields have been reported to increase growth or healing or otherwise modify the structure of various tissues, including nerves, bones and skin. Systematic application of these techniques in both animal research and clinical treatment has been hampered by the limitations of currently available technology. We describe a new modular approach in which one or more wireless, microminiature, programmable current generators can be injected or implanted in a wide range of sites. Each device has its own address and can be powered and commanded via an external RF field to produce 10, 100 or 500 μA DC and/or pulse trains of 0.2-30 mA at 4-512 μs duration. The implants are 2 mm in diameter and 16 mm long. They are made from hermetically sealed, biocompatible materials, so they can be used indefinitely or left in situ after treatment is complete.