Insulin and insulin resistance have attracted considerable interest as possible risk factors for coronary heart disease during the last decade. We therefore examined the 8-year incidence of coronary heart disease in 595 67-year-old men in relation to baseline insulin and other risk factors. The incidence of coronary heart disease increased from 9% among non-diabetic men to 13.5% among those with impaired glucose tolerance, 12.9% among newly-detected diabetic men and up to 31.3% among men with known diabetes. The incidence of coronary heart disease was related to fasting blood glucose and 1 h and 2 h blood glucose during the oral glucose tolerance test and to serum cholesterol and serum triglycerides. Fasting serum insulin was of borderline significance for the risk of coronary heart disease. When known diabetic subjects were excluded only serum cholesterol and serum triglycerides remained as statistically significant risk factors. Among diabetic subjects (known and newly-detected) only blood glucose was related to the risk of coronary heart disease. In multivariate analyses the different degrees of glucose intolerance or fasting blood glucose were independently related to the risk of coronary heart disease (p = 0.008-0.010). Serum triglycerides were also an independent risk factor in three out of four multivariate models (p = 0.02-0.09). Fasting serum insulin was not an independent risk factor. These findings do not support the hypothesis that hyperinsulinaemia is a major risk factor for coronary heart disease in elderly men. Hyperglycaemia (or diabetes mellitus) seems to be the most important risk factor.