Introduction: Insulin resistance has been implicated in the pathogenesis of essential hypertension. Elevated blood pressure during physical exercise is a more powerful predictor of future hypertension than resting blood pressure. We have therefore studied the relationship between insulin resistance and blood pressure response to exercise in strongly hypertension-prone subjects. Material: Twenty-five normotensive subjects aged 18-35 years with bi-parental hypertension, and 26 matched controls with normotensive parents. Methods: (i) Maximal exercise tolerance test with continuous gas-exchange measurement; (ii) blood pressure at rest, during exercise and 24-h ambulatory; (iii) euglycemic hyperinsulinemic clamp. Results: Diastolic blood pressure during exercise was higher in hypertension-prone subjects as compared to controls, but only in subjects with low insulin sensitivity. Resting and 24-h diastolic blood pressure were higher in hypertension-prone subjects, but independent of insulin sensitivity level. Insulin sensitivity and exercise capacity were similar in the groups. Conclusion: Diastolic blood pressure during exercise was higher in hypertension-prone subjects as compared to controls, but only in insulin-resistant subjects. Since elevated blood pressure during physical exertion is a predictor of future hypertension, these findings may suggest that insulin resistance is involved in the pathogenesis of essential hypertension.