To investigate the role of RAD51, XRCC3, and XRCC2 in breast cancer predisposition and to identify putative recurrent founder mutations in the Finnish population where such mutations have been observed in most of the currently known susceptibility genes, we screened 182 familial Finnish breast or ovarian cancer patients for germline variation in the RAD51and XRCC3 genes and 342 patients for variation in XRCC2, with a subset of the patients selected on the basis of decreased RAD51 protein expression on tumors. This evidence concerns the gene XRCC3 and breast carcinoma.