This study was undertaken to evaluate the status of margins of the excised breast tissue using our own method. We also determined the indications for breast-conserving surgery without irradiation by examining the characteristics of patients with local recurrence and comparing relapse-free survival (RFS) and overall survival (OS) of patients who underwent wide excision without irradiation with those of 267 patients who underwent total mastectomy. Eighty-two patients with a 3 cm diameter or less invasive carcinoma were treated with wide excision and axillary dissection between 1987 and 1996. Patients who histologically had four or more axillary lymph node metastases, positive pathologic margins, or a high degree of in situ ductal carcinoma around the main tumor in consecutive step-sections were excluded from this study. During a median follow-up of 6 years (range 2-11 years), six patients (7.3%) had local recurrence and five (6.0%) had regional or distant recurrences as their site of first failure. At 11 years the life-table values for RFS and OS for the wide excision-treated group were 84.7% and 92.1%, respectively, compared with 85.0% and 90.0%, respectively, for patients treated by total mastectomy. RFS and OS were similar in the two treatment groups. Results in the present study indicate that if the patients treated by breast-conserving surgery are carefully selected and there are no foci in the pathologic margins, there is a low degree of in situ ductal carcinoma around the tumor, and no multicentricity, it might be unnecessary to administer