The objectives of this study were (a) to evaluate the dose-response effect of isradipine, a dihydropyridine calcium antagonist, on the heart rate and blood pressure of males with mild to moderate hypertension; and (b) to compare these results with those obtained with propranolol, a beta-adrenoceptor blocker, on a matched patient population. Twenty-four patients entered a single-blind study, beginning with a 2-week washout placebo period followed by a forced-titration period. Treadmill and hand-grip tests were also performed. Two weeks were allocated to each stage of the therapy. The end point of the study was normalization of blood pressure with a minimum of side effects. Results and conclusions include the following: both drugs were effective in reducing systolic blood pressure (SBP) and diastolic blood pressure (DBP), but isradipine was more effective in reducing the DBP; isometric exercise can predict accurately the results of the isotonic exercise; the maximum therapeutic effect of propranolol was achieved during the second study-dose level; increases in the isradipine dose were reflected in a proportional reduction of SBP and DBP; and the incidence of side effects is lower among isradipine-treated patients compared to propranolol-treated patients.