Few studies have examined the relation of blood pressure reactivity to subsequent change in blood pressure of preschool children. The authors investigated relations between measurement-induced reactivity, exercise reactivity, and change in blood pressure over 16 months among 140 preschool children (46-67 months of age at baseline, 50.7% female, 92.9% Hispanic). Within-session measurement-induced reactivity was defined as the change in blood pressure between the first and the mean of the fourth and fifth readings obtained at each of 11 sessions. Between-session measurement-induced reactivity was defined as the change between mean blood pressure at session 1 and the mean of sessions 2 and 3. Both indices of measurement reactivity displayed poor reproducibility. Exercise reactivity was measured using a treadmill on two occasions and was moderately reproducible. There was no association between measurement and exercise reactivity. The change in systolic blood pressure over time was not associated with any measure of reactivity. The mean diastolic blood pressure did not change over the study period. Neither blood pressure reactivity to measurement nor blood pressure reactivity to exercise appeared to be a useful predictor of change in blood pressure in preschool children during a 16-month period.