Cilnidipine is a dihydropyridine calcium antagonist. In the present study 14 hospitalized patients with essential hypertension were administered cilnidipine and 24 hour ambulatory BP was monitored. Once daily administration of cilnidipine 5 20 mg for a period of 1 3 weeks was noted to reduce 24 hour average BP significantly from 149 4 88 2 mmHg to 141 3 82 2 mmHg without any change in the pulse rate. The decrease in ambulatory BP was more evident during daytime 156 4 93 2 mmHg to 143 5 84 2 mmHg while it was mild during nighttime 141 4 80 2 mmHg to 133 4 76 3 mmHg . The reduction in ambulatory BP over the whole day and during nighttime significantly correlated with basal ambulatory BP levels. After segregating the subjects into high ambulatory BP n 7 and low ambulatory BP n 7 groups the BP reduction with cilnidipine was evident throughout 24 hours in the high ambulatory BP group while it was mild and significant only during daytime in the low ambulatory BP group. Once daily cilnidipine was thus found to exert a sufficient and prolonged reduction of BP without an increase in pulse rate in patients with hypertension. Cilnidipine is an effective antihypertensive drug that may not lead to excessive decrease in BP or a reflex tachycardia. The findings were published in Cardiovascular Drugs and Therapy.