Niludipine (Bay a 7168), a newly developed Ca2+-antagonist, was administered to eight aged patients with moderate to severe hypertension in order to study the antihypertensive effects and duration of action of a single dose as well as to evaluate the long-term effects. The subjects in the present study consisted of eight hypertensive, hospitalized patients (four men and four women, average age 74.6 years). After a two-week control period niludipine was administered in doses of 60 or 120 mg daily for five consecutive weeks (drug period) and, then, placebo tablets were administered in the same number of tablets as that of the drug for one week. On the first day of the treatment period, the drug was administered three times in a dose of 20 mg each, and the blood pressure and pulse were measured for 10 h after the administration. The systolic blood pressure was significantly reduced in the second and subsequent weeks of the treatment period, while the diastolic blood pressure was reduced only in the fourth week (P less than 0.05). During the placebo period, the blood pressure was elevated again. No side-effects were noted. In the single dose study, the systolic blood pressure was significantly reduced within 4 h after the administration, reaching its lowest value after 6 h, and tended to return to the pretreatment level after 10 h.