This proposes to establish and operate a Clinical Unit in the NCI's Multicenter randominized clinical trial of the efficacy of a diet low in fat (20% of calories) in the prevention of breast cancer in women with increased risk for breast cancer. The trial's primary objective is to determine if the low-fat diet can decrease the incidence of breast cancer. This application proposes the unit's participation in all three phases of the Trial by the cooperative agreement mechanism: development of the protocol in two months, the feasibility trial of ten months, and the full-scale trial of 48 months. The Baylor Clinical Unit will consist of the Baylor Lipid Research Clinic working in collaboration by subcontract with the Breast Cancer Detection Center of St. Joseph's Hospital. For the feasibility and full scale trials, the Unit will study a cohort of 200-240 patients recruited from the Breast Cancer Detection Center according to the protocols criteria. The unit will collaborate with the Trial's other Clinical Units, Nutrition Coordinating Unit, Statistical Coordinating Unit, and the NCI. The Baylor Unit's major aims include: 1) To operate the Clinic Unit with economy and accuracy using a micro-computer assisted surveillance and management of clinic operations and quality control of data. 2) To gain maximum dietary adherence for this efficacy trial using a combination of standard and innovative techniques, including selection of subjects with high potential for adherence by an adherence screening examination and washout criteria, individual counseling by trained Dietitian/Adherence Counselors trained in counseling techniques developed by the Baylor Lipid Research Clinic aided by immediate analysis of the patient's 7-day food record by the micro-computer based Nutrient Analysis System and multimedia instruction by food models, cooking demonstrations, slide tapes, newsletters, and bulletin boards. Adherence counseling is based upon the identification, diagnosis of and management of adherence problems using behavioral techniques and frequent counselor-patient contact. 3) To evaluate methods of diet recording, 24-hour diet recall, 1-7 day diet self-recording, and objective measures of diet adherence as body weight, skin fold thickness, plasma total cholesterol, and HDL cholesterol, and the proportion of linoleic acid in the plasma cholesteryl esters. The optimum methods of clinical trial operation, adherence management and surveillance, from the feasibility trial will be applied to the full-scale trial. The project's significance is a potential for developing a dietary method for prevention of cancer in women at high-risk of breast cancer.