A metastasis from a bronchial carcinoid tumor presented as an isolated breast mass in a 58-year-old female. A review of the English literature revealed four cases of metastatic carcinoid to the breast that presented as an isolated breast mass. In each case, radical mastectomy was performed after the lesion had been interpreted clinically and pathologically as a primary carcinoma. When the primary tumor was excised, all cases had either regional lymph node or liver involvement. A mass was the usual presenting sign of the metastatic deposit. No metastasis was reported to be greater than 2 cm in diameter. No axillary lymph nodes were reported to contain tumor. Frozen section preparations may not be adequate to differentiate a primary carcinoma of the breast from a metastatic carcinoid tumor, thereby necessitating permanent sections, special stains, review of previously resected neoplasms, or electron microscopy. The first mammogram of a metastatic carcinoid to the breast is reported with this case. Cancer 40:3102-3106, 1977.