Mutations in the tumor suppressor genes BRCA1 and BRCA2 account for a small percentage of breast cancer cases. In an Advanced Online Publication from Nature Genetics, researchers from the CHEK-Breast Cancer Consortium report the identification of a mutation in the CHEK2 gene that increases the risk of breast cancer in both women and men (22 April 2002, DOI: 10.1038/ng879). They performed a genome-wide linkage search in a family with BRCA-independent breast cancer and identified a mutation in the CHEK2 gene that results in a truncated protein. CHEK2 is a cell-cycle checkpoint kinase involved in DNA-damage-response pathways. The mutation abolished kinase activity, and is five times more frequent in families affected by breast cancer who do not have BRCA1 or BRCA2 mutations.