The relation between blood pressure level and reactivity to mental arithmetic and isometric exercise was investigated in 169 men and 120 women (average age, 32.3 years) from the village of Tecumseh, Mich. In the entire population, the correlation between baseline blood pressure and blood pressure response to both stressors was not significant. Blood pressure reactivity to both stressors was not increased in participants with borderline hypertension (one clinic reading of more than 140 mm Hg systolic and/or 90 mm Hg diastolic). When subjects were classified according to blood pressure response (below and above the 80th percentile), the hyperreactors to mental and physical stress had normal baseline blood pressure values. The hyperreactors also had clinic-to-home blood pressure differences similar to those of the rest of the population. Participants who had borderline hypertension at age 32 years had significantly elevated blood pressures at ages 5, 8, 12, 21, and 22 years. Those who were hyperreactors at age 32 years had normal blood pressures as children and young adults. Results of the present study lend no support to an association between higher blood pressures and blood pressure hyperreactivity. Study participants in Tecumseh will be recalled for future examinations. The independence of blood pressure levels from blood pressure reactivity offers a unique opportunity to prospectively evaluate their separate effects on cardiovascular morbidity.