An international collaborative group examined the relation between asymptomatic hyperglycemia and coronary heart disease (CHD). After excluding clinically diagnosed diabetes and treated hypertensives, there were 48,912 men aged 35-64 in the study population. Post-load circulating glucose correlated with age, relative weight, and systolic blood pressure. The prevalence on ECG of S-T/T findings, but not of Q/QS items, was higher in the top quintile of glycemia. For CHD mortality there was no consistent, strong, or independent association with glycemia. In the Whitehall Study (the largest), it appeared that there was a threshold effect, CHD mortality being about twice as high above the 95th percentile of glycemia. Stroke mortality was increased to a similar extent.