In the present study, the frequencies of the Colombian founder mutations (BRCA1/A1708E, BRCA1/3450del4, BRCA2/1991del4, BRCA2/3034del4) in 1,022 unselected breast cancer cases were 5.5% for BRCA1 and 1.5% for BRCA2. No mutations were identified in 1,023 controls. The gene discussed is BRCA1; the disease is breast carcinoma.