Of 176 patients with minimal breast cancer, 138 had intraductal carcinoma in situ, 21 minimally invasive carcinoma, and 17 lobular carcinoma in situ. Various modalities of treatment were used including radical, modified radical, and simple mastectomy with and without radiation therapy. Long-term postoperative follow-up was available in all but five patients and ranged from one year to twenty-one years. Actuarial analysis projected a twenty year survival of 93.2 per cent for the entire group. Analysis of survival figures based on each of the several treatment modalities showed no definite advantage of one form of treatment over another. The data suggest that minimal breast cancer is a prognostically favorable diagnosis, provided invasive carcinoma is not present or does not develop in the opposite breast. It is also indicated that breast cancer is potentially a bilateral disease and that follow-up and treatment of the opposite breast must be of major concern in the care of these patients.