Analysis of genetic predisposition to cancer can provide valuable information for early cancer detection or even prevention. Insertion 5382insC in BRCA1 gene is the most frequent mutation among those associated with high risk of breast cancer in women of East European origin. The method of 5382insC detection using fluorescent labeled allele specific oligonucleotides in Duplex Scorpion format has been developed. The method can be used in real-time PCR conditions as well as in conditions of end-point fluorescence measurement followed regular PCR. The adequacy of the method was demonstrated in the study of 5382insC mutation frequency in breast cancer patients. 564 samples of genomic DNA from breast cancer patients were genotyped. Eleven patients (1.95%) were found to be heterozygous for BRCA1 5382insC mutation. 5382insC allele frequency in breast cancer patients group was 0.0098. The method can be used as in clinical practice to determine individuals of a high risk of breast cancer, as in wide-scale population studies.