Nonunion of the long bone is one of the difficult porbloems in orthopaedic surgery. We studied the effect of the electrical stimulation. From July, 1980 to August, 1988, 30 nonunions of the long bones were treated with the invasive type electrical stimulator. The range of follow-up period was from 3 months to 7 years(average, 25 months). The results were as foloowings: 1. The good bony union has occurred in 26 cases(86.7%). 2. The previous infection was in 11 cases and its union rate was 100% 3. The average duration of bone union in over-all cases was 5. months and in previous infeted cases, was 5.5 months. 4. The average duration of bone union in open fracture was 5.5 months and in closed fracture, was 5 months. 5. The invasive electrical stimulation was a good technique to treat the intractable nonunion as the result of long bone fracture.