A user-friendly feedback-controlled diode laser system for tissue welding will be developed and applied to nerve anastomosis. Rapid reliable nerve anastomosis has numerous applications. In cancer therapy, removal of tumors in head and neck region frequently requires subsequent repair of the facial nerve. In reconstructive surgery of the hand after trauma, multiple microanastomoses are needed. In oral surgery, removal of lower wisdom teeth can result in nerve injury requiring microsurgery to repair damaged peripheral nerves. The prototype nerve anastomosis system will use feedback control to obtain more consistent welds than are possible with manual control. The prototype system will be mounted on an operating microscope and will use a micromanipulator to deliver focused light to the nerve. Feedback control will be based on using the backscattered light from the irradiated tissue to determine when collagen denaturation has occurred. Studies of the polarization, angular distribution, and relative change in specular and diffuse backscatter will be conducted to determine the optimum control technique. An acute study using the rat sciatic nerve will be used to determine the optimum tissue welding parameters. A chronic study using a rabbit model will then compare conventional and laser anastomoses, as evaluated by electrophysiological and quantitative histomorphometric assays.