Twenty-three essential hypertensive and 22 normotensive middle-aged men participated in a controlled exercise program for six months; the effect the program had on blood pressures (taken while the men were resting) was determined. There was no other change in therapeutic management during the exercise training period. The exercise medium used was the interval training of the walkjog type, with training intensity based on the actual heart rate expressed as percent of working capacity. A drop in mean diastolic pressure of 11.8 mm Hg and in mean systolic pressure of 13.5 mm Hg occurred in the hypertensive group. There was a mean decrease of 6 mm Hg in the diastolic pressure of the normotensive group, but no significant change in the mean systolic pressure.