The incidence of breast cancer in women has been rising dramatically inthe United States since 1982, based on data collected by the Surveillance, Epidemiology, and End Results (SEER) program of the National CancerInstitute. An additional three years of incidence and mortality data areincluded in this update of the earlier analyses; however, the focus of thisreport remains on examining the steeply increasing incidence trend between1982 and 1986. Over this period, incidence rates for in situ and localizedinvasive tumors increased among women age 50 and older, while rates forregional and distant tumors remained stable. The incidence of localizedtumors less than 1.0, 1.0 to 1.9, and 2.0 to 2.9 cm in size increased morerapidly than that of tumors 3.0 cm and greater among women over age 50.Survival rates also improved among cases diagnosed over this time period.These descriptive data suggest that early detection may be playing a rolein the recent increase in the incidence of breast cancer in women, althoughother factors cannot be ruled out. Conclusions regarding improved cancercontrol await confirmation by reduced breast cancer mortality.