A high plasma renin activity (PRA) has previously been related to several cardiovascular risk factors as well as to later cardiovascular events. As insulin resistance has been suggested as the unifying factor in the insulin resistance metabolic syndrome, insulin resistance was evaluated by the euglycaemic hyperinsulinaemic clamp technique in 50 untreated hypertensive subjects in whom PRA and serum aldosterone were measured together with lipids and an intravenous glucose tolerance test (IVGTT). PRA was inversely related to insulin-mediated glucose disposal during the clamp (r=-0.31, P < 0.05), as well as to fasting insulin (r=0.32, P < 0.05) and to insulin at 60 min at the IVGTT (r=0.30, P < 0.05), but not to other risk factors. Serum aldosterone was not related to any of the metabolic risk factors. In conclusion, the present investigation showed that insulin resistance is associated with elevated levels of PRA in patients with untreated essential hypertension. It thus seems as if a high activity in the renin system should be included in the disturbances included in the insulin resistance metabolic syndrome, a syndrome with a major impact on future cardiovascular events.