Fourteen hypertensive patients and 14 normotensive control subjects were submitted to the oral glucose test and their plasma potassium, glucose and insulin levels were measured. Cardiovascular responses were evaluated by blood pressure and pulse rate measurements. Five of 14 hypertensive patients were hyperinsulinemic and had higher blood glucose levels, suggesting insulin resistance. Systolic blood pressure, heart rate and double product increased significantly in normotensive subjects and slightly in hyperinsulinemic patients, but not in normoinsulinemic hypertensive patients. These results seem to indicate the presence of insulin resistance in a particular group of primary hypertensive patients and a smaller cardiovascular response after glucose overload.