In 165 women with breast cancer who were candidates for mastectomy because the largest diameter of the tumor was 3 cm or more, we administered primary chemotherapy in the attempt to substitute conservative for mutilating surgery. We then systematically quantitated tumor reduction by clinical, radiologic, and histopathologic evaluations. Five consecutive groups of 33 patients received cyclophosphamide, methotrexate, and fluorouracil (CMF); fluorouracil, doxorubicin (Adriamycin), and cyclophosphamide (FAC); or fluorouracil, epirubicin, and cyclophosphamide (FEC). The regimens for the five groups were as follows: group 1, three cycles of CMF; group 2, four cycles of CMF; group 3, three cycles of FAC; group 4, four cycles of FAC; and group 5, three cycles of FEC. In response to primary chemotherapy, 157 of the 161 assessable patients showed measurable tumor shrinkage; progressive disease was documented in four. Tumor shrinkage to less than 3 cm was documented in 127 (81%) of the 157 women subjected to surgery, thus allowing a breast-saving procedure, rather than modified radical mastectomy, in these 127 women. Histopathologic complete remission was documented in seven patients. Tumor response was unrelated to age, menopausal status, DNA content (ploidy), [3H]thymidine-labeling index, drug combination used, or number of treatment cycles in excess of three. The degree of response was inversely proportional to the initial tumor size, and the frequency of response was greater in receptor-negative tumors. Severe vomiting and hair loss were less frequent with CMF than with anthracycline-containing regimens, and the frequency of severe leukopenia and thrombocytopenia was minimal. Our results challenge the classical indication for primary mastectomy by showing that use of full-dose primary chemotherapy, sequentially combined with conservative surgery and radiation, can offer an effective and safe alternative to women concerned about the preservation of body integrity.