-edited) The Dallas County Familial Breast Cancer Registry at UT Southwestern Medical Center will comprise a population-based repository of clinical data, demographic and pedigree information as well as biological specimens obtained from breast cancer families and appropriate controls. The biological specimens to be stored in this repository will include serum, extracted DNA, lymphoblastoid cell lines, cryopreserved mononuclear cells, paraffin block specimens and, in some instances, fresh tumor and normal tissue materials. The registry is designed to facilitate collaboration involving the identification and characterization of new genes which predispose to breast cancer. Funding of this application will facilitate correlation of genetic predisposition factors with demographic and reproductive risk factors. The registry extends the already existing UT Southwestern Familial Cancer Registry, a joint effort of UT Southwestern Medical Center; Texas Oncology, PA, a large private practice network of oncology specialist; Baylor University Medical Canter, a large private hospital; and the Susan G. Komen Breast Cancer Foundation. This unique partnership, known as """"""""The Komen Alliance"""""""" has to date identified and analyzed over 300 families with a probable predisposition to breast cancer. The population base to be studied will correspond to Dallas County, Texas, a population of 2 million which includes approximately 1080 new cases of breast cancer annually. We will attempt to screen every newly diagnosed case of breast cancer in Dallas County over a two-year period and will strongly encourage participation by women thought to have a familial form of breast cancer in the Familial Breast Cancer Registry.