PURPOSE: We have used the proximal femoral nailing (PFN(R)) to evaluate the result of treatment for unstable femoral peritrochanteric fractures. MATERIALS AND METHODS: From December 2000 to December 2001, 20 patients who had femoral peritrochanteric fracture were treated with proximal femoral nail (PFN(R)) in our hospital. The mean duration of follow-up was 16.8 months and average age was 58.7 years old. We evaluated the ambulation time, bone union time, neck-shaft angle, neck screw sliding by follow-up radiography, and studied the intra-operative and post-operative complication. RESULTS: The average ambulation time was 3.8 days, the mean bone union time was 20.9 weeks, the mean neck shaft angle was 130.2 degree at post-operative time and 128.8 degree at last follow-up time, and the average neck screw sliding distance was 4.1 mm. The intra-operative complication was rotation of proximal fracture fragment in 1 case and displacement of femoral greater trochanter in 2 cases at proximal reaming, and displacement of proximal fracture fragment in 1 case at femoral stem insertion. The post-operative complication was coxa vara deformity in 2 cases and superficial wound infection in 1 case. CONCLUSION: We have conclude that the proximal femoral nail (PFN(R)) could appropriately treat the unstable femoral peritrochanteric fracture and we obtained satisfactory results.