The relationship between blood pressure and the blood sugar concentration measured two hours after a 50 g oral glucose load has been examined in two population surveys-the Whitehall and Bedford Surveys. In the Whitehall Survey, which was conducted in men above the age of 40, there was a positive, significant correlation between blood sugar and blood pressure (systolic and diastolic) which was independent of common associations with age, body mass index (BMI) and heart rate. In the Bedford Survey, systolic blood pressures were significantly higher in newly detected diabetics and borderline diabetics, both men and women, than in normoglycaemic controls after adjustment of blood pressures for age and BMI. However, in the stratified random sample of the cooperating Bedford population, only amongst women was the blood sugar significantly and independently correlated with the systolic blood pressure. Evidence is presented and discussed that autonomic, neurohumoral factors may play some part in the pathogenesis of maturity onset diabetes.