Thirty-nine patients with mild to moderate essential hypertension participated in a parallel, single-blind study comparing 6 weeks' treatment of nicardipine hydrochloride (90 mg/day) with nifedipine (40 mg/day). Nicardipine-treated patients commenced therapy with a significantly higher mean supine diastolic blood pressure than the nifedipine-treated patients. There was a statistically significant fall in blood pressure (systolic and diastolic) on both treatments at the 3 and 6 week follow-up visits. On adjusting the results for the baseline inequality, no statistically significant differences were found between treatment groups. Seven patients withdrew from nifedipine therapy and six patients withdrew from nicardipine therapy due to adverse events. The results show that nicardipine hydrochloride at 90 mg/day is an effective anti-hypertensive agent. The incidence and nature of adverse events were similar on the two treatments.