The effectiveness and tolerability of captopril and verapamil SR were compared in a double-blind, crossover study in 23 elderly hypertensives [15 males and 8 females, aged (mean +/- SEM) 68 +/- 1 years]. After 2 weeks of placebo run-in, patients were randomized to a starting dose of captopril, 12.5 mg b.i.d. or verapamil SR, 120 mg q.d. plus matched placebo of the opposite drug. Medication was titrated up over 6 weeks to a maximum dose of 75 mg of captopril or 360 mg of verapamil SR to achieve a sitting diastolic blood pressure of < 90 mm Hg. After 2 weeks of placebo washout, captopril and verapamil were crossed over. In the 20 patients who completed the study, the dose at the end of the respective treatment periods averaged 63 +/- 4 mg of captopril and 270 +/- 21 mg of verapamil SR. Blood pressure at the end of the run-in and washout placebo periods were comparable: 164 +/- 4/97 +/- 1 and 163 +/- 4/98 +/- 2 mm Hg, respectively. However, the blood pressure was significantly lower after verapamil, i.e., 147 +/- 4/86 +/- 2 mm Hg, than after captopril, i.e., 155 +/- 4/90 +/- 1 mm Hg (p < 0.05, ANOVA). There was no significant change in heart rate and laboratory parameters and no orthostatic hypotension. Captopril-treated patients reported a positive change in well being compared with placebo, although there was no overall difference between the drugs in any of the ten quality of life measurements. Three patients discontinued treatment, two because of constipation (verapamil) and one due to lack of efficacy (captopril).(ABSTRACT TRUNCATED AT 250 WORDS)