The pharmacokinetic variables of sufentanil were studied in 20 healthy children between two and eight years of age. The plasma concentrations of sufentanil were measured for up to 480 min after administration of a bolus of sufentanil, 1-3 micrograms.kg-1. The distribution half-life (t1/2 alpha) was 5.2 +/- 2.2 (mean +/- SD) min and the elimination half life (t1/2 beta) was 97.0 +/- 42.0 min. The volume of distribution at steady state (Vdss) was 2.9 +/- 0.6 L.kg-1 and the clearance was 30.5 +/- 8.8 ml.kg-1.min-1. The Vdss was one and a half times greater than that reported in adults when expressed as a function of body weight but similar to that of adults when expressed as a function of body surface area. According to our results, the clearance of sufentanil in normal children between two and eight years of age is twice as rapid as that described in adults and adolescents. A greater clearance of sufentanil in children suggests that they would require relatively greater maintenance doses than adults.