Purpose: We reviewed the outcome of treatment of ossifying fibroma involving long bones. Materials and methods: Eight patients who enrolled at our hospital for ossifying fibroma from 1994 to 1999 were selected for this study. Mean age was 7.9 years old. Five were male and three female. Seven involved tibia and one fibula. All cases were diagnosed by biopsy. The initial treatment was conservative and the followings were operative indications; (1) repeated fracture, (2) suddenly growing mass, (3) severe bowing deformity, (4) pseudoarthrosis. We assessed the recurrence by x-ray follow-up. Results: As initial treatment, curettage was performed in 2 patients, observation in 2 subperiosteal resection in one and extraperiosteal resection in 3 patients. Two patients who were observed and 3 patients who received extraperiosteal resection did not suffer recurrence. Two patients who received curettage and one patient who received subperiosteal resection had recurrence. The second treatment was performed in 3 patients. The one case of curettage received extraperiosteal resection. The other was in observation. The case of subperiosteal resection was in observation, too. There were no recurrence and aggravation at follow-up. Conclusion: Ossiying fibroma should to be treated by conservative method. If operation is indicated, extraperiosteal resection could reduce the recurrence.