OBJECTIVE: To evaluate the dosage and effectiveness of isradipine to control acute or chronic hypertension in pediatric patients. DESIGN: Retrospective medical record review. SETTING: University teaching hospital. PARTICIPANTS: Hospitalized pediatric patients aged 1 day to 16 years with hypertension treated with isradipine between January 1994 and March 1996. MEASURES: Patient age, gender, weight, disease states, current medications, isradipine dosage and formulation, pre- and postsystolic, and pre- and postdiastolic blood pressure measurements with each dose of isradipine. RESULTS: Fifty-three patients with a mean age of 5.8 ± 4.0 years were evaluated. A mean change in the blood pressure measurements taken before the first dose of isradipine compared with the values recorded after the last dose or at discharge for all patients was -11.8% ± 12.5% and -17.4% ± 19.6%, respectively, for systolic and diastolic pressure. The mean dosage of isradipine in 46 patients who received regularly scheduled doses was 0.38 ± 0.22 mg/kg/d. Patients who demonstrated a response received a mean dosage of 0.40 ± 0.20 mg/kg/d. The total daily dosage was administered in one dose for 1 patient, two doses for 15 patients, three doses for 27 patients, and four doses for 3 patients. CONCLUSIONS: Isradipine was an effective antihypertensive agent to reduce the systolic and/or diastolic blood pressure 10% or more compared with pretreatment measurements in 43 (81%) of 53 pediatric patients. The mean dosage was 0.38 ± 0.22 mg/kg/d, most frequently administered in two or three equally divided doses, which is higher than the normal recommended dosage for adults.