Inhaled furosemide has been shown to attenuate bronchospasm in asthmatics and to increase lung compliance in infants with bronchopulmonary dysplasia (BPD). The reports involving BPD used a dose of 1 mg/kg and some have failed to show an effect with that dose. We determined the pharmacokinetics of furosemide administered directly to the airway in 7 young adult male guinea pigs who received intravenous and intratracheal doses of furosemide. Each animal received a 3 mg/kg i.v. bolus, 1, 3 and 6 mg/kg i.t. in 2 ml/kg normal saline and 3 mg/kg i.t. in 2 ml/kg bovine extract surfactant. Blood was sampled multiple times after each dose. The mean fraction of the intratracheal dose absorbed was 0.50-0.60 for all doses. Surfactant delayed the absorption of furosemide but did not alter the fraction absorbed.