Breast cancer incidence in the United States has been rising dramatically since 1982, as shown in data collected by the Surveillance, Epidemiology, and End Results (SEER) Program. In women aged 50 and older, incidence rates for in situ and localized invasive tumors have increased over the period 1982-86, while rates for regional and distant tumors have remained stable. The incidence of localized tumors less than 1.0 cm, 1.0-1.9 cm, and 2.0-2.9 cm in size has increased more rapidly than that of tumors 3.0 cm or more in size among women over age 50. Survival rates also have improved among cases diagnosed over this time period. These data suggest that early detection may be playing a role in the recent increase in female breast cancer incidence, though other factors cannot be ruled out. Conclusions regarding improved cancer control await confirmation by reduced breast cancer mortality.