Fifty-two black men who had supine diastolic blood pressures (DBP) above 95 mm Hg at the end of a 2-week placebo wash-out period were randomized to receive either isradipine SRO at 2.5 mg/day or enalapril at 10 mg/day for 8 weeks. After 4 weeks, the dosages were doubled if DBP remained above 90 mm Hg. Reductions in blood pressure were comparable in both groups. Mean supine DBP was reduced from 100.6 to 93.9 mm Hg in the isradipine-treated group, and from 103.9 to 98.2 mm Hg in the enalapril-treated group. At the end of the study, 24/27 patients were taking 5 mg isradipine SRO once daily, and 20/25 patients were taking 20 mg enalapril once daily. There were no serious adverse events. The results of this study indicated that monotherapy with isradipine SRO at the recommended initial dosage of 5 mg once daily is appropriate in black patients with hypertension. This was, however, not the case with enalapril at 10 mg once daily. The concurrent administration of a diuretic with enalapril may be more appropriate.