Exogenous surfactant therapy has been recognised as an approach to alleviating the surfactant-deficine state for 3 decades. Natural and lipid-extracted surfactants derived from amniotic fluid, lung lavage, or lung homogenates are being used in worldwide clinical trials in premature infants. These studies are demonstrating a generally favourable influence on lung function by improving oxygenation and reducing the risk for pneumothorax and pulmonary interstitial emphysema. In some studies, reduction in death and the occurrence of bronchopulmonary dysplasia have been found. Numerous questions are unresolved and pharmacokinetic data are limited in preterm infants. Artificial surfactants are similarly under evaluation but current data demonstrate less overall effect. Adult respiratory distress syndrome has also been treated with exogenous surfactants. Although complex in terms of multiple initiating factors and in terms of high permeability of surfactant inhibitors, further studies are under way to determine the ideal methods of administration to enhance distribution and to monitor surfactant function in vivo.