Previous studies showed the importance of the response of blood pressure to emotional stress in essential hypertension. However, it is unclear to what extent the response of blood pressure to emotional stress is influenced by antihypertensive treatment, and especially by beta-blockers. In the present study the influence of antihypertensive treatment with either beta-blockers (beta) or diuretics (D) was compared in two series of experiments on male hypertensives, carried out after 2 weeks (beta, n = 11; D, n = 11) and 1 year of treatment (beta, n = 11; D, n = 9). One of the two drugs was randomly allocated to each patient. In the first series of experiments an ergometric exercise test was also performed (workload depending on age and body surface area, 60-100 W). The two medications caused a similar decrease in basal blood pressure. The response of blood pressure to emotional stress was also the same in both groups, and equal to that in untreated hypertensives. However, the reaction of systolic blood pressure to dynamic exercise was lower in the patients treated with beta-blockers (30.2 +/- 9.5 mm Hg) than in those treated with diuretics (42.9 +/- 12.1 mm Hg; p = 0.013). The effect of antihypertensive treatment on the reactivity of blood pressure therefore cannot comprehensively be tested by means of a single stress test. In terms of controlling the response of blood pressure to stress, beta-blockers are not generally more effective than diuretics, but only in certain situations.