The influence of exercise on the relationship beween the 0.1 Hz variability in systolic blood pressure and pulse intervals with respect to the baroreflex sensitivity was studied. A causal interrelationship between the 0.1 Hz variability of systolic blood pressure and pulse intervals and baroreflex sensitivity was shown. During exercise, an increased variability of systolic blood pressure might be a sign of an increased sympathetic activity, and it explaind a relatively hyigh PI variability in some subjects at low BRS.