Ventricular arrhythmias occur frequently in patients with hypertensive left ventricular (LV) hypertrophy and have been associated with increased incidence of sudden death. In this study, the effect of various antihypertensive medications on ventricular arrhythmias was evaluated in 31 hypertensive patients with moderate to severe LV hypertrophy. Patients were assessed at baseline (after 3 weeks of placebo treatment) and after treatment with each of 4 monotherapies: diltiazem 120 or 240 mg/day, metoprolol 100 or 200 mg/day, enalapril 10 or 20 mg/day and hydrochlorothiazide 50 or 100 mg/day. Each drug therapy was administered for 4 weeks. The sequence of each treatment was determined at random. Echocardiographic measurements and electrocardiograms were obtained only at baseline. Biochemical measurements and 48-hour Holter monitoring were obtained at baseline and at the end of each treatment. All treatments resulted in a significant but similar decrease in blood pressure. In the group as a whole diltiazem decreased ventricular premature complexes (VPCs) by 65% (p < 0.05) and metoprolol by 52% (p = 0.07). Enalapril and hydrochlorothiazide had no effect. In 12 patients with > or = 5 VPCs/hour at baseline, diltiazem and metoprolol decreased VPCs by 66% (p < 0.05). It is concluded that in hypertensive patients with moderate to severe LV hypertrophy, both diltiazem and metoprolol significantly reduce VPCs.