In a population study of 6956 middle-aged men, 5% received drug treatment for hypertension, another 25% had a blood pressure of greater than 160.90 mmHg, and 3.2% were diabetic. Prevalence of impaired glucose tolerance and diabetes was two- to threefold in hypertensive subjects, and 50% of the glucose intolerant or diabetic cases had hypertension. In 4677 unselected subjects without clinical coronary heart disease or previous diabetes, estimated insulin resistance (i.e. the 2-h insulin-to-glucose ratio during an oral glucose tolerance test, controlled for body mass index) correlated with both systolic and diastolic blood pressure. In untreated subjects, a diastolic blood pressure of greater than 90 mmHg was found in conjunction with a higher insulin resistance value than predicted, whereafter blood pressure progressively increased. The contribution of drug treatment to insulin resistance was significant, but less than 1% in the whole material and about 2.5% in cases with impaired glucose tolerance.