The report examines geographic variation in the onset of the decline of ischemic heart disease (IHD) mortality in white males aged 35-74 during the period 1968-78. Using a quadratic regression model, State Economic Areas (SEAs) were classified as experiencing onset of the decline in 1968 or earlier, 1969-72, or 1973 or later. In the United States as a whole, approximately one-third of SEAs experienced a late onset of the decline (after 1968). Metropolitan SEAs were in advance of non-metropolitan, and the Northeast and Pacific states showed earlier onset than the South and midsections of the country. The acceleration of the national decline after 1972 appears to be due to declines in areas in which rates had been increasing or in plateau until that time. Evidence about geographjic variation in the onset of decline may provide clues about social and environmental factors responsible for the decline. (Copyright (c) 1986 American Journal of Public Health.)