In this clinical study the efficacy and tolerability of lisinopril and sustained-release (SR) verapamil hydrochloride were compared in black patients with mild-to-moderate uncomplicated essential hypertension. The goal of therapy was to achieve a supine diastolic blood pressure (SDBP) of less than 90 mmHg or a greater than or equal to 10-mmHg fall in SDBP. Forty-three patients completed the titration phase, 23 in the lisinopril group and 20 in the verapamil SR group. The mean baseline supine systolic/diastolic blood pressures were 147/98 mmHg for the lisinopril group and 155/100 mmHg for the verapamil SR group. At the end of a two- to eight-week titration period, 87% of the lisinopril-treated patients and 90% of the verapamil SR-treated patients had achieved SDBP control. Six patients were excluded from maintenance therapy: four in the lisinopril group (one because of urticaria and three because of failure to reach goal blood pressure) and two in the verapamil SR group (because of failure to reach goal blood pressure). After eight weeks of maintenance therapy, 68% of the lisinopril-treated patients and 72% of the verapamil SR-treated patients had achieved SDBP control. The mean decreases in SDBP were comparable for both treatment groups. At the end of titration, the mean decreases from baseline were 10.5 mmHg for the lisinopril group and 12.6 mmHg for the verapamil SR group. At the end of maintenance, the mean decreases from baseline were 7.8 mmHg for the lisinopril group and 9.2 mmHg for the verapamil SR group. Adverse experiences were few.(ABSTRACT TRUNCATED AT 250 WORDS)