This multicenter trial compared the efficacy and safety of isradipine and enalapril in 160 patients with essential hypertension. Patients received isradipine or enalapril for 10 weeks after a placebo wash-out period of three to five weeks. Dosage was titrated for six weeks on the basis of blood pressure (BP) response and was then maintained for the remainder of the study. Isradipine reduced systolic and diastolic BP by 12 and 9 mm Hg, respectively, and enalapril by 10 and 7 mm Hg, respectively (between-treatment difference P less than .05 for diastolic BP). Overall, isradipine resulted in a higher responder rate, particularly among patients who had higher entry BPs. Fifteen enalapril-treated patients and four isradipine-treated patients discontinued treatment (four taking enalapril and none taking isradipine withdrew because of lack of efficacy). The most frequently reported adverse reactions were headache, dizziness, and edema in the isradipine group, and cough, headache, and chest pain in the enalapril group. Both drugs produced significant reductions in BP, but, in this study isradipine was more effective. The drugs were similarly well tolerated.