Fifty cases of Paget's disease of the breast treated surgically at The Johns Hopkins Hospital during the past 30 years were studied. Nineteen patients had Paget's disease confined to the nipple and 31 had an associated palpable tumor. An underlying intraductal or infiltrating duct carcinoma of the breast was present in each case. In six cases, the underlying tumor was 2 cm or more from the nipple with no apparent anatomic connection to the Paget lesion, and one case was encountered in whom intradermal Paget's disease develop in the area of a congenitally absent nipple. These findings support the theory of an intradermal origin for the Paget cell. Survival rates of patients with Paget's disease and a palpable breast mass were similar to those of patients with infiltrating duct carcinoma, the presence of axillary node metastases being the most important prognostic factor. Actuarial five- and ten-year survival rates were 22% and 9.9% for patients with positive nodes. The modified radical mastectomy is recommended as primary therapy for this group of patients. In contrast, none of the patients with Paget's disease of the nipple and no evidence of a palpable breast mass developed recurrent carcinoma. A total mastectomy without an axillary node dissection is the treatment of choice in this type of patient.