1. Resting carotid baroreflex sensitivity and blood pressure responses to standardized conditions of rest and exercise were measured in 17 borderline hypertensive males and 12 normotensive males.
2. The borderline hypertensive group had significantly higher systolic and diastolic blood pressures during orthostatic rest and isometric handgrip exercise and higher systolic blood pressure during supine rest and submaximum and maximum treadmill exercise.
3. The borderline hypertensive group had an attenuation of baroreflex sensitivity compared with the normotensive group. Resting baroreflex sensitivity was significantly correlated with absolute systolic blood pressure during supine rest, orthostatic rest, isometric handgrip exercise and submaximum treadmill exercise.
4. The results indicate that blood pressure is regulated at a significantly higher level during rest and exercise in borderline hypertension and is associated with reduced baroreflex sensitivity measured at supine rest.