Breast cancer incidence and mortality measured for the population of a major metropolitan center included 7368 cases and 2357 deaths over 15 years, ascertained according to National Cancer Institute Surveillance, Epidemiology, and End Results program procedures. Occupational risks were estimated with a census-based occupation coding system for cases and deaths, mean annual age-standardized rates, and age-truncated occupation allocation. Data limitations include absence of population frequencies of personal risk factors for breast cancer, occupation designation errors, lack of knowledge about chemical exposures in apparently high-risk occupations, and the possibility that the number of comparisons could produce significant differences by chance. Compared to community-wide reference incidence and mortality rates, significant excess breast cancer risks were identified for housewives, registered nurses, clinical laboratory technicians, schoolteachers, social workers, secretaries and typists, and meat wrappers and cutters. High incidence rates with unremarkable mortality rates were identified for dental hygienists, religious workers, electronic engineering technicians, authors and journalists, restaurant and bar managers, realty and insurance saleswomen, bank tellers and cashiers, telephone operators, canning and bottling workers, chemical and gas handlers, and papermill workers. These findings agree in part with similar reports and will contribute to the generation of hypotheses to be tested by more specific, in-depth studies.