The single-dose pharmacokinetics of dexamethasone were studied in 7 extremely low birth weight infants of mean (+/- SD) gestational age 25.6 +/- 0.5 weeks suffering bronchopulmonary dysplasia. A mean peak dexamethasone concentration of 250.5 +/- 70.7 ng/ml was obtained following an intravenous bolus dose (0.369 +/- 0.04 mg/kg dexamethasone) of dexamethasone sodium phosphate. Dexamethasone was measured in plasma by HPLC. Mean clearance (0.143 +/- 0.028 litres/kg/h) was approximately half that reported previously in children and adults, while the half-life (9.26 +/- 3.34 h) was 2- to 3-fold longer than in these patients. The volume of distribution (1.9 +/- 0.483 litres/kg) was larger than reported in a previous study in adults, but was similar to that determined in pediatric and adult patients in another study.