Eight preterm infants were given intravenous nicardipine, a calcium channel blocker, to treat systemic hypertension (renal artery thrombosis (n = 3); dexamethasone for management of bronchopulmonary dysplasia (n = 2); unexplained (n = 3). Nicardipine doses ranged from 0.5 to 2.0 micrograms/kg/min and were given for three to 36 days (mean (SD) 15.9 (10.3) days). Systolic blood pressure had significantly decreased after 12 and 24 hours of nicardipine treatment (-17 (17)% and -21 (10)%, respectively). Diastolic blood pressure significantly decreased after 24 hours of treatment (-22 +/- 16%). The decrease in blood pressure remained significant over the subsequent days of treatment. No hypotension or other clinical side effects were observed. It is concluded that intravenous nicardipine could be a first line treatment for hypertension in preterm infants.