Plasma glucose and insulin responses to an oral glucose challenge and insulin-stimulated glucose uptake were measured in 47 age-, weight-, and sex-matched lean white men (16 with normal blood pressure, 14 with untreated hypertension, nine treated with a thiazide diuretic only, and eight treated with combined diuretic and β-adrenergic antagonist drugs). Following a 75-g glucose dose, plasma glucose and insulin were measured for a three-hour period. In separate studies, insulin-stimulated glucose uptake was estimated by measuring the steady-state plasma glucose (SSPG) and insulin (SSPI) concentrations achieved during the last 30 minutes of a 180-minute continuous infusion of somatostatin, insulin, and glucose (insulin suppression test). Under these conditions endogenous insulin secretion was suppressed, and differences in SSPG concentration allowed comparisons of the abilty of exogenous insulin to stimulate disposal of an identical glucose load in different individuals. The results indicated that men with untreated hypertension had significantly elevated plasma glucose (P < .001) and insulin concentrations (P < .001) after an oral challenge compared to normal volunteers. Mean SSPG concentrations were also higher (P < .05) than normal in patients with untreated hypertension. Furthermore, plasma glucose and insulin concentrations after the oral glucose challenge and SSPG concentration during the insulin suppression test were higher in treated than in untreated patients with hypertension. These results confirm earlier observations that untreated patients with hypertension are insulin resistant, hyperglycemic, and hyperinsulinemic compared to a well-matched normotensive control group, and suggest that conventional treatment programs for lowering blood pressure many exaggerate these metabolic defects. Am J Hypertens 1989;2:419 – 423