Background: To evaluate the efficacy of tamoxifen as primary treatment in women aged over 70 years with operable breast cancer versus surgery followed by adjuvant tamoxifen. Patients and methods: Patients randomly received tamoxifen alone (160 mg day 1, then 20 mg/day) for 5 years or surgery followed by tamoxifen (20 mg/day) for 5 years. Overall survival was the main study end point; secondary objectives included breast cancer survival and local control of the disease. Results: Between 1987 and 1992, 239 patients were assigned to surgery plus tamoxifen and 235 to tamoxifen alone. Treatment arms were comparable for tumor size, clinical nodal status and performance status. At a median follow-up of 80 months 274 patients had died. No difference between groups had emerged in overall and breast cancer survival. There were 27 local progressions in the surgery plus tamoxifen group and 106 in the tamoxifen-alone group (P = 0.0001). In the surgery plus tamoxifen group, no difference in overall survival had emerged according to the extension of operation. Conclusions: The long-term results of the study confirm the 3-year interim analysis already reported. Surgery (radical or minimal) followed by adjuvant tamoxifen does not modify overall and breast cancer survival as compared with tamoxifen alone in early breast cancer of older women. Because of the high rate of local progressions with tamoxifen alone, minimal surgery followed by tamoxifen appears to be the appropriate treatment in such patients. More extensive surgery is not useful. Tamoxifen alone is an adequate alternative treatment in very old or frail patients.