The four most common BRCA1 mutations in Latin American breast cancer patients are: the ex9-12del mutation (1.45%) found in Mexican Americans and Mexicans, but not in Spaniards and South Americans19, 21, 26; 185delAG (0.9%) is found in many different regions of Latin America including Argentina, Brazil, Chile, Mexico and Peru; A1708E (0.58%) is found in Mexico, Spain and Colombia (one of the Colombian founder mutations)11, 18, 27; 3450del4 (0.15%), finally, is identified in patients from Brazil, Chile and Colombia (one of the Colombian founder mutations). This evidence concerns the gene BRCA1 and breast cancer.