Twenty-five patients with tubular carcinoma of the breast were reviewed. All of the lesions were small, averaging 0.9 cm in diameter, and none exceeded 2.0 cm in diameter. Regardless of treatment, the prognosis proved favorable. Only three of the patients manifested axillary lymph nodal metastases, and none died of recurrent or metastatic neoplasm. These neoplasms frequently were associated with intraductal carcinoma and, to a lesser extent, with lobular carcinoma in situ. It is concluded that tubular carcinoma represents a slow-growing expression of invasive mammary carcinoma; nevertheless, it is likely that, if inadequately treated, these lesions will evolve into more common patterns of invasive carcinoma.