The optimal treatment for ductal carcinoma in situ (DCIS) of the breast is undefined. At three Connecticut hospitals 1) Yale-New Haven Hospital, New Haven; 2) Uncas-on-Thames Hospital, Norwich; 3) Norwalk Hospital, Norwalk, breast conservation therapy with lumpectomy followed by radiation therapy (RT) has been offered to women with DCIS as an alternative to mastectomy. From 1974 through 1987, 60 women with DCIS have been treated with RT. With a minimum evaluable follow-up of two years, a maximum follow-up of 15 years, and a median follow-up of 3.6 years, there have been no cancer-related deaths in the 60 patients. Four of the 60 patients (6.7%) developed a local breast recurrence but were salvaged with further surgical therapy (three patients with mastectomies and one patient with repeat lumpectomy). Only one patient (2%) has died of nonmalignant disease and the remaining 59 patients (98%) survived cancer-free. The five-year actuarial breast recurrence-free rate was 95%. These results suggest that breast conservation therapy with RT is a viable treatment option for women with DCIS.