Little is known about dopamine pharmacokinetics in pediatric patients, especially in critically ill infants and children who often receive treatment with dopamine. Arterial plasma concentrations of dopamine were measured in 27 patients who were hemodynamically stable and received dopamine for at least one hour. The dopamine levels were measured using liquid chromatography with electrochemical detection. Dopamine clearance averaged 96.2 +/- 55.4 ml/kg.min in 13 patients in the neonatal ICU, and 58.8 +/- 51 ml/kg.min in 14 patients in the pediatric ICU. Six patients had renal (BUN greater than 25 mg/dl, or creatinine greater than 1.2 mg/dl) or hepatic (liver enzymes greater than 3 times normal) dysfunction. Dopamine clearance in these patients (25.1 +/- 17.2 ml/kg.min) was substantially lower than in the other patients (p less than .01). Neither postnatal nor gestational age correlated with dopamine clearance. Substantial interindividual variation was observed in steady-state dopamine clearance in critically ill infants and children, and plasma dopamine could not be predicted accurately from the dopamine infusion rate. Because of the more than three-fold prolongation of dopamine clearances in patients with hepatic or renal dysfunction, these patients may be more likely to suffer toxic effects of dopamine at the usual drug infusion rates.