Our aim was to devise a practical strategy that could be applied at the time of diagnosis for identifying, with high sensitivity and specificity, those young women with early-onset breast cancer who have the highest probability of carrying a germline mutation in BRCA1. We used morphological and immunohistochemical data that could be routinely collected at diagnosis, as well as data on family history of breast cancer in first- and second-degree relatives. The gene discussed is BRCA1; the disease is breast carcinoma.