The proposed study is a response to an RFA to study the effect of fat reduction on disease-free survival and on overall survival in women with Stage II breast cancer. Seven Chicago institutions: Northwestern University, University of Chicago, Michael Reese, St. Francis Hospital, Mercy Hospital, Evanston Hospital, and Rush-Presbyterian-St. Luke's have agreed to participate. Expected accrual from these institutions is 80 patients per year for three years, for a total of 240 patients. It is proposed that data management for the Chicago Center be coordinated through the Illinois Cancer Council (ICC) with the diet intervention coordinated by the Department of Community Health of Northwestern University. They propose to utilize the knowledge and expertise gained in previous cardiovascular diet intervention trials, such as the Multiple Risk Factor Intervention Trial. Issues about the specific study design, such as recruitment, eligibility criteria, dietary intervention, and statistical methods are discussed in the proposal.