A clinical investigation has been carried out into the effect of small electrical currents on the healing of mandibular fractures. Electrical stimulation of fracture healing was carried out in 40 patients with a direct current of 10 or 20 microamperes delivered through a platinum electrode. An equal number of patients with similar fractures were selected as controls. Rate of repair was assessed by measuring the mobility of the fracture. Serum phosphatase and calcium were regularly measured at intervals in both groups after reduction and suggested that alkaline phosphatase activity increased in the stimulated group. The repair process was enhanced in the electrically stimulated fractures compared to the controls in the first 10-14 days after reduction.