We performed presymptomatic carrier detection by BRCA gene testing of the family members of three familial breast cancer kindred diagnosed with pathogenetic mutation in BRCA genes. All members were over 20 years of age. We explained familial breast cancer and BRCA gene testing, and obtained autonomic consent before gene testing. Genetic testing revealed twins in a family were dizygotic. In another family bilateral breast cancer occurred in a carrier after five years of genetic testing. Carriers are at high risk of breast cancer and have to receive breast cancer screening and familial tumor counseling. Non-carriers are at the same risk of breast cancer as the general population.