In this study we genotyped Turkish breast/ovarian cancer patients for BRCA1/BRCA2 mutations: protein truncation test (PTT) for exon 11 BRCA1 of and, multiplex PCR and denaturing gradient gel electrophoresis (DGGE) for BRCA2, complemented by DNA sequencing. In addition, a modified restriction assay was used for analysis of the predominant Jewish mutations: 185delAG, 5382InsC, Tyr978X (BRCA1) and 6174delT (BRCA2). Eighty three breast/ovarian cancer patients were screened: twenty three had a positive family history of breast/ovarian cancer, ten were males with breast cancer at any age, in eighteen the disease was diagnosed under 40 years of age, one patient had ovarian cancer in addition to breast cancer and one patient had ovarian cancer. All the rest (n=30) were considered sporadic breast cancer cases. Overall, 3 pathogenic mutations (3/53-5.7%) were detected, all in high risk individuals (3/23-13%): a novel (2990insA) and a previously described mutation (R1203X) in BRCA1, and a novel mutation (9255delT) in BRCA2. In addition, three missense mutations [two novel (T42S, N2742S) and a previously published one (S384F)] and two neutral polymorphisms (P9P, P2532P) were detected in BRCA2. Notably none of the male breast cancer patients harbored any mutation, and none of the tested individuals carried any of the Jewish mutations. Our findings suggest that there are no predominant mutations within exon 11 of the BRCA1 and in BRCA2 gene in Turkish high risk families., (Copyright 2003 Wiley-Liss, Inc.)