The frequencies of four mutations in the BRCA1 gene (185delAG, T300G, 4153delA, and 5382insC) were estimated in the Russian population. The mutations were analyzed in 7920 DNA samples obtained from randomly selected Novosibirsk citizens and 570 samples from breast cancer patients at Siberian hospitals. The mutations were detected by allele-specific real-time PCR. The mutation analysis was performed with pooled DNA samples to reduce the cost of the study. The 5382insC mutation was found in 20 of 7920 (0.25%) population DNA samples and in 14 of 570 (2.46%) breast cancer samples; the T300G mutation was detected in 4 population samples (0.05%) and in 2 breast cancer samples (0.35%); the 185delAG or 4153delA mutations were not identified in any of the 7920 samples and were detected in 1 (0.18%) breast cancer case each.