The hypotensive action of CV-4093.2HCl (CV-4093), a new calcium antagonist, was studied in spontaneously hypertensive, renal hypertensive, DOCA-salt hypertensive and normotensive rats. CV-4093 (3 and 10 mg/kg, p.o.) dose-dependently decreased systolic blood pressure in the three types of hypertensive rats. At the dose of 10 mg/kg, the compound decreased the blood pressure to the normotensive level between 1 and 3 hr after it was administered; the antihypertensive effect lasted for at least 8 hr. The systolic blood pressure in normotensive rats was also decreased at 3 and 10 mg/kg, p.o., but less evidently than in the hypertensive rats. When the antihypertensive effect of CV-4093 was compared with that of seven known calcium antagonists in spontaneously hypertensive rats, it was the most potent and the most long-lasting.