Men who inherit a mutation in the BRCA2 gene carry a 6% risk of developing breast cancer by the age of 70. The proportion of male breast cancers attributable to BRCA mutations has not yet been determined with accuracy. We studied a series of 14 male breast cancer patients, unselected for family history or ethnicity, who were treated at a single regional cancer center in Canada. Family histories were obtained, and the men were tested for germ-line mutations of BRCA1 and BRCA2. Seven of these patients had a significant family history of breast cancer (i.e., at least one first- or second-degree relative with breast cancer diagnosed before age 70). Two of the men carried BRCA2 mutations, but no BRCA1 mutations were found. Both mutation carriers reported a positive family history and a personal history of cancer that preceded their diagnosis of breast cancer. Our results support the recommendation that male breast cancer patients who have a significant family history of breast or ovarian cancer should be offered genetic counseling and testing.