All fine-needle aspirates (FNA) performed on the male breast at The University of Texas M. D. Anderson Cancer Center from 1985 to 1992 were reviewed, totaling 64. The patients' ages ranged from 19 to 86 years, with a mean of 56 years. Thirty-three patients had a history of an extramammary malignancy. The diagnoses established by FNA were gynecomastia (45), mammary carcinomas (6), neoplasms metastatic to the breast (5), suspicious for carcinoma (1), intra-mammary lymph node (1), and lipoma (1). In five cases the aspirates were nondiagnostic. Two of these proved to be gynecomastia on subsequent histologic examination. Of the six FNA cases initially thought to represent primary breast carcinomas, two were found to be secondary because of involvement of the underlying chest wall by mesothelioma (1), and mucinous adenocarcinoma, unknown primary (1). No false-positive diagnosis was rendered. We conclude that fine-needle aspiration of the male breast is a reliable means of assessment; however, unique problems may be encountered compared with aspiration of the female breast. These include the epithelial hyperplasia frequently associated with gynecomastia, the relatively equal frequency of primary and metastatic breast lesions when a malignant process is discovered, and chest wall lesions masquerading as breast lesions.