Most studies of secretory carcinoma of the breast have been single case reports or separate analyses of the problem in either children or adults. We studied 10 female patients, aged 5 to 87 years. Most patients presented with a palpable mass, often near the areola. Five of six tumors were estrogen receptor negative; three analyzed for progesterone receptor were positive. Histologic patterns present in varying proportions were "classic" secretory carcinoma with microacini, abundant secretion with papillary features, and with prominent solid and papillary apocrine features. The tumors had strong reactivity for alpha-lactalbumin, S100, and carcinoembryonic antigen (polyclonal) and were negative for gross cystic disease fluid protein and anti-carcinoembryonic antigen (monoclonal). Six patients had mastectomy; four had local excision; none had axillary nodal metastases initially. With follow-up of 3 to 72 months (mean, 47 months; median, 48 months), two patients treated by local excision had local recurrences, one patient had axillary nodal metastases. All patients are alive. Comparison of patients under and over 30 years of age revealed one important difference: younger patients had a longer interval between detection and biopsy-30 vs 2 months. Treatment recommendations are initial wide excision or quadrantectomy with low axillary dissection in most cases and, in premenarchal patients, strong effort to preserve the breast bud without jeopardizing local control.