A case of carcinoma in the breast of a male patient with a chronic gastric ulcer is described. The patient had received cimetidine for 17 years. Histological examination of an excisional biopsy showed lobular in situ and infiltrating carcinoma. In our review of the English literature, this is the 18th case of lobular carcinoma of the male breast to be reported; it is also the first report of lobular carcinoma associated with the use of cimetidine, and the second in a man with documentation of genotype.