Although coronary heart disease is a leading cause of morbidity and mortality among persons with diabetes, the risk factors for coronary heart disease have not been well established for this population. The authors performed a case-control analysis by using data from two large population-based surveys. Cases of persons who died of coronary heart disease were identified from the 1986 National Mortality Followback Survey, and controls were taken from behavioral risk factor surveys conducted in 35 states in 1988. Diabetic women younger than 55 years with no other risk factors for coronary heart disease had a 16-fold higher risk of dying from coronary heart disease than did women without diabetes. About one-third of younger women who died of coronary heart disease had diabetes. Diabetic men less than 45 years old with no other risk factors for coronary heart disease had an eightfold higher risk of coronary heart disease mortality. Among older white men and women, diabetes increased the risk of mortality from coronary heart disease about twofold. In younger diabetics, current cigarette smoking was associated with a 50% increase in risk, and high blood pressure increased the risk more than threefold. In the older age group, risk factors for coronary heart disease mortality were similar among those with and those without diabetes: Cigarette smoking and high blood pressure each were associated with about a twofold increase in risk. Diabetes is a particularly strong risk factor for mortality from coronary heart disease in young adults. Smoking and blood pressure control represent major opportunities to reduce the risk of coronary heart disease among persons with diabetes.