In 1979, a prospective, randomized trial was begun at the National Cancer Institute comparing lumpectomy, axillary dissection, and radiation therapy (XRT) to modified radical mastectomy for the treatment of invasive breast cancer, clinical stage T1-2, N0-1, M0. Treatment in the radiation arm consisted of full axillary dissection and gross removal of the tumor, followed by 4500 to 5000 cGy to the whole breast and a boost to the tumor bed of 1500 to 2000 cGy. Patients with positive axillary dissections received radiation to the supraclavicular nodes, in addition to cyclophosphamide and doxorubicin. Two hundred thirty-seven patients entered in the trial between 1979 and 1987 are available for analysis, 116 in the mastectomy arm and 121 in the radiation arm. With a median follow-up of 67.7 months, there are no significant differences in 5-year overall survival (85% vs 89%, mastectomy vs radiation) or 5-year disease-free survival (82% vs 72%, mastectomy vs radiation). Patients in the radiation arm had an actuarial in-breast recurrence rate of 12% at 5 years and 20% at 8 years. There were no major differences between complication rates in the treatment arms. The results of the study indicate that patients with invasive breast cancer, stage I and II, can be treated with lumpectomy, axillary dissection, and radiation therapy with results comparable to those with modified radical mastectomy.