This study proposes to assess the risk of breast cancer associated with various constellations of histologic, sociologic, genetic, environmental and demographic variables in women who have presented with benign breast disease. A study group of 5,800 women is available for analysis. These women were selected on the basis of histologic criteria without knowledge of their subsequent breast cancer history. Follow-up questionnaires were sent to these women to ascertain whether they developed breast cancer, and to learn about their non-anatomic risk factors. These risk factors include family history of breast cancer, age of menarch, age of menopause, menstrual status, age of entry biopsy, pregnancy and breast feeding history, estrogen usage, gynecologic surgery, tobacco and alcohol consumption, etc. The length of follow-up varies between ten and 27 years. We propose to elucidate the interactions between these risk factors and breast cancer using proportional hazards regression analyses, multivariate categorical data analyses and cluster analyses as well as standard epidemiologic techniques. We will use as our primary control group women who presented with low risk non-hyperplastic breast lesions at Baptist Hospital in Nashville during the recruitment years of our study. We will also use Third National Cancer Survey data from Atlanta and data from the Cancer in Connecticut series to form two standard populations for further comparisons with our study group.