To assess the value of exercise stress testing and of mental stress as predictors of hypertension, we studied 130 normotensive males 14-18 years of age. Sixty-five had at least one hypertensive parent (SHT), while 65 had normotensive parents (SNT). Systolic (SBP) and diastolic (DBP) blood pressure, rate-pressure product (RPP) and 12-lead ECG were recorded at rest, throughout the tests and during the recovery phase. The two groups were not significantly different at rest for the examined variables. However, the SHT group showed a greater average SBP than the SNT group (198.4 +/- 18.7 vs 189.5 +/- 14.9 mmHg; P less than 0.05) at the peak of exercise. A significantly higher proportion of SHT subjects (40.0% vs 18.5%: P less than 0.01) had SBP greater than 200 mmHg. No difference in the ECG pattern between the two groups was observed. During mental stress, no significant differences in the examined variables between the two groups were noted, although SBP, DBP, HR and RPP were slightly higher in SHT than in SNT subjects. These data suggest that the SBP response to dynamic exercise may be a good predictor of hypertension in subjects at risk.