To evaluate the outcome of pts treated with Breast-Conserving Surgery (BCS) and definitive irradiation (DR) for Ductal Carcinoma in situ of the breast (DCIS). 110 cases (104 evaluable) treated between 1980 and 1990 have been collected in 9 Italian Institutions. All the cases were treated with BCS (quadrantectomy 78, wide excision 8, tumorectomy 18) and DR (median breast total dose 50 Gy, median boost dose 10 Gy). Median follow up time was 62 months (range 21–151). There were 6 (5.7%) failures in the breast. Neither nodal recurrences or distant metastases were observed. All the 6 patients were salvaged with mastectomy. Five metachronous controlateral breast tumors (2 invasive) and 4 second tumors developed during follow-up. Five-year actuarial overall, cause specific and breast-recurrence free survival is 94.6%, 100% and 90% respectively. This study confirm that RCS and DR is an effective alternative to mastectomy in the treatment of DCIS of the breast.