Objective:To assess the relationship of insulin levels and glucose tolerance to blood pressure in hypertension.Design:An open, prospective trial of exercise training with ambulatory blood pressure monitoring and intravenous glucose tolerance testing before and after a 14-week training programme.Patients:Twenty sedentary, untreated, non-obese, normoglycaemic individuals of both sexes with uncomplicated essential hypertension, of whom 16 completed the study.Intervention:Fourteen weeks of supervised, low-intensity, group exercise of three 1-h sessions per week.Main outcome measures:Ambulatory and clinic blood pressure, and glucose and insulin responses to an intravenous glucose tolerance test.Results:Maximal work capacity on a bicycle ergometer increased by 20% (P< 0.001); 24-h ambulatory blood pressure was 143 ± 12/87 ± 5 mmHg before and 142 ± 13/87 ± 7 mmHg after training. Clinic blood pressure decreased from 166 ± 14/103 ± 5 mmHg to 157 ± 12/99 ± 6 mmHg (P< 0.03). Two-way analysis of variance indicated significant decreases in both glucose (P< 0.04) and insulin (P< 0.03), fasting and throughout the intravenous glucose tolerance test.Conclusions:Although mild exercise reduced clinic blood pressure significantly, it did not affect ambulatory blood pressure despite a marked reduction in glucose and insulin levels. This finding argues against a determinant role of insulin in the 24-h maintenance of blood pressure in hypertensive patients under the conditions of the study.