This paper presents long-term results from a randomized trial of pre- or postoperative megavoltage radiation therapy versus surgery alone in pre- and postmenopausal women with operable breast cancer. Treatment outcome after relapse among patients who developed loco-regional recurrences was also analyzed. A total of 960 patients were included in the trial. The mean follow-up was 16 years (range: 13-19 years). The radiation therapy was individually planned. It included the chest wall (and the breast in the preoperative cases) and the regional lymph nodes. The tumor dose was 45 Gy/5 weeks. No adjuvant systemic therapy was used. The results showed a significant benefit with radiation therapy in terms of recurrence-free survival during the entire follow-up period. There was also an overall survival difference-corresponding to a 16% reduction of deaths-in favor of the irradiated patients which, however, was not statistically significant (p = 0.09). Among those 169 patients who developed locoregional recurrences long-term control was only achieved in about one-third of the cases. This figure was similar among those who had received adjuvant radiation therapy (34%) compared to those initially treated with surgery alone (32%). This implied that the overall proportion of patients who eventually developed uncontrolled local disease was significantly higher among those initially allocated to surgery alone (16%) compared to those allocated to pre- or postoperative radiation therapy (6%, p < 0.01). These results suggest that local undertreatment may be deleterious in subgroups of patients.