A retrospective case-control hospital study of 785 Caucasian breast cancer patients and 2,231 age-stratified controls was conducted in New York City from 1969-1975. Patients were grouped by pre- peri- and postmenopausal status at diagnosis for the analysis to make a distinctive separation for variables showing a pre- and postmenopausal differential. Demographic characteristics were similar for cases and controls. Previously recorded hormone-related risk variables for this disease were largely confirmed for pre- and perimenopausal women, i.e., late age at first birth (greater than 25), premenstrual symptoms of breast swelling and premenopausal chills and flushes. Mother's history of breast cancer was also found to be a risk variable. Nulliparity was a risk factor only perimenopausally. No risk was foun for absolute height, weight or for obesity (Quetelet Index), prior breast diseases or previous usage of exogenous hormones of any type and no "protective" effect was found for multiparous women and for nursing. Perimenopausally diagnosed patients (menopause to 10 years after) were similar to premenopausally diagnosed women on most risk factors. Risk variables determined by this and other case-control studies cannot account for the magnitude of differences in the international incidence of breast cancer.