I examine the problem of the management of the opposite breast of a patient with ipsilateral carcinoma, reviewing the literature from the standpoint of the incidence of carcinoma in the contralateral breast, autopsy studies, blind biopsy results, and other factors such as age and multicentricity. In my series of 343 cases of carcinoma of the breast, there were 110 cases (32%) of bilateral mastectomy; 47 (43%) showed carcinoma in only one breast, 40 (36%) exhibited contralateral carcinoma, and 23 (21%) showed Consensus Added Risk Factors (CARF). The remaining 233 cases of carcinoma of the breast were treated by unilateral mastectomy. In 59 of these cases of bilateral mastectomy in which a prophylactic contralateral mastectomy had been performed, 15% showed carcinoma of the opposite breast and 22% showed CARF. In 51 cases, the contralateral mastectomy had been performed for clinical or radiographic indications. Of this group, 61% showed carcinoma and 20% showed CARF. All of my studies are based on routine pathologic studies and not on any specialized, subserial whole organ studies. © 1990 Southern Medical Association.