Germline mutations in the BRCA1 and BRCA2 genes predispose to breast and ovarian cancer. A variable incidence of mutations has been reported for these genes. The contribution of BRCA1 and BRCA2 mutations to Mexican women with breast and/or ovarian cancer is not known. Because of the increasing prevalence of breast cancer in this population, it is necessary to study the presence of mutations in both genes. We screened BRCA1 and BRCA2 genes in 40 patients: 29 patients with a history of breast and/or ovarian cancer, and 11 patients with early-onset breast cancer (< 40 years), through denaturing high performance liquid chromatography analyses. We found two frameshift mutations in BRCA1 and one missense mutation in each gene. Additionally we found several intronic variants as well as synonymous mutations. We found 5% of deleterious mutations in the BRCA genes. Larger studies are needed to establish the significance and prevalence of BRCA mutations among Mexican women.