We studied the acute antihypertensive effect of sublingually administered nifedipine in 21 patients with different clinical diagnoses. Nifedipine lowered systolic and diastolic BP from 181 +/- 18 and 136 +/- 21 mm Hg to 132 +/- 15 and 98 +/- 17 mm Hg, respectively, after 30 minutes, and produced a slight increase in heart rate. This is the first known study of administration of nifedipine for acute hypertension in children.