The risk of breast cancer for unaffected men who test positive for a BRCA2 mutation is based on very few retrospective studies. We have used both retrospective and prospective analysis in 321 families with pathogenic BRCA2 mutations. Three breast cancers occurred in male first-degree relatives after family ascertainment in 4140 years of follow-up suggesting a risk of breast cancer to 80 years of 8.9%. A second analysis excluding index cases identified 16 breast cancers in 905 first-degree male relatives on which Kaplan-Meier analysis was performed after assigning carrier status. This analysis confirmed that breast cancer risk in men was 7.1% (SE 5.2-8.6%) by age 70 years and 8.4% (SE 6.2-10.6%) by age 80 years.