We analyzed the complete coding sequence and boundaries of pre-miR-16, pre-miR-182, pre-miR-192, and pre-miR-146a in 99 probands who had a strong family history of BC, but were negative for BRCA1 and BRCA2 point mutations, with the aim of identifying new miRNA sequence variations in a Chilean population. The gene discussed is BRCA1; the disease is breast cancer.