Only about 40% of the familial aggregation of breast cancer can be attributed to germline mutations in currently identified genes, primarily BRCA1 and BRCA2. A recent genome-wide association study focusing on Jewish Ashkenazi high risk women identified a novel locus on chromosome 6 as putatively containing breast cancer susceptibility genes, a locus that contains two seemingly novel candidate genes: RNF146 and ECHDC1. To further explore the role of these two genes in inherited predisposition to breast cancer. High risk, cancer affected Jewish Ashkenazi women, were genotyped for harboring germline mutations in the coding exons of both the RNF146 and ECHDC1 genes, using direct sequencing. All participants were Ashkenazim, of high risk families, and affected with cancer: 104 with breast cancer [age at diagnosis (mean +/- SD) 51 +/- 11.1 years], and one with ovarian cancer (61 years). None was a carrier of the predominant Jewish BRCA1/BRCA2 mutations. An intronic sequence alteration was detected in 4/105 genotyped patients in intron 3 of the ECHDC1 gene. No other sequence alterations were detected in the genomic regions analyzed of the RNF146 and ECHDC1 genes in any of the study participants. Mutations in the coding regions of the RNF146 and ECHDC1 genes do not contribute to the burden of inherited predisposition of breast cancer in Ashkenazi high risk women.