Ten variants different from the canonical nucleotide sequence (GenBank, U14680) has been identified when studying the mutation spectrum in gene BRCA1. Six of them (5382insC, 2963del10, 3819de15, 3875del4, 2274insA, and R1203X) cause premature termination of protein synthesis, thus predisposing to breast cancer. A missense mutation E1250K is presumed to be a factor of predisposition to cancer. We classified three variants of nucleotide sequence found in some patients as DNA polymorphisms S694S, L771L, and E1038G. The 5382insC and 3819de15 mutations have been detected in four and two families, respectively. Five of the mutations detected have not been found in Russia before. However, all mutations except for 2963del10 have been found in other populations of the world, which indicates their long evolutionary history. Two mutations found in patients from St. Petersburg (5382insC and 3875de14) have also been found in oncological patients from other regions of the Russian Federation.