PURPOSE: To evaluate the effects of surgical excision followed by radiation therapy for prevention of keloids and hypertrophic scars. MATERIALS AND METHODS: From October 1987 to April 1995, radiation therapy was applied to 167 sites in 106 patients with surgical excision in an attempt to prevention of recurrence against keloids and hypertrophic scars. The main etiology of the keloids and hypertrophic scars were surgery in 49.2%, trauma in 25.0%, ear-piercing in 5.4%, and burn in 5.4%. The patients' ages ranged from 3 to 70 years with a median of 32 years. Radiation therapy used ranged from 6 to 8MeV electron beam. Radiation therapy was delivered within 24 hours of surgical excision. Several dose schedules were used, varing from 400cGy in 1 daily fraction to 1900cGy in 4 daily fractions. The average total dose was 1059cGy, and the average dose per fraction was 433cGy. All patients were followed up from 24 to 114 months with a median follow up of 49 months. RESULTS: The overall recurrence rate was 12.6% (21/167). The overall 1-year and 2-year recurrence rates were 10.2% and 11.4%, respectively. Among 21 recurrent sites, seventeen sites (81%) were confirmed within 12 months after surgical excision. Period to recurrence ranged from 1 month to 47 months with a median recurrence time of 9.6 months. The history of previous therapy was only a significant factor in recurrence. Twenty-four patients had history of previous therapy, recurrence rates was significantly higher in this group than those without history of previous therapy (22.6% vs. 11.0%, P=0.04). There was no serious complication related to radiation therapy. CONCLUSION: This study suggests that surgical excision followed by radiation therapy is an effective method of preventing keloids and hypertrophic scars.