To assess the efficacy, tolerability and pharmacokinetics of verapamil in the elderly, ten patients with blood pressure greater than 160/90 mmHg were studied in a randomized double-blind placebo-controlled cross-over trial. Nine patients aged 75 (+/- 4.9) years completed the study. After titration, doses of verapamil varying from 40 to 120 mg (40 mg in four, 80 mg in one and 120 mg in four patients) twice daily for six weeks were taken. Mean (+/- SEM) clinic lying blood pressure was reduced on verapamil from 187 +/- 6.8/100 +/- 4.1 to 167 +/- 4.6/86 +/- 3.1 mmHg, [P less than 0.001). Mean ambulatory blood pressure was reduced from 174 +/- 1.4/95 +/- 1.0 to 169 +/- 1.3/90 +/- 0.8 mmHg, (P less than 0.01). Lying heart rate was significantly reduced but glomerular filtration rate, renal blood flow and mental function, were not altered by treatment. The mean plasma half-life of verapamil was 6.9 +/- 1.1 hours. Side effects were minimal. We conclude that verapamil is an effective blood pressure lowering agent in the elderly.