Six critical patients aged 2 months to 13 years with lung diseases were treated by pulmonary surfactant preparation. Three of these children developed the acute respiratory distress syndrome in the presence of grave pneumonia (1 case), asphyxial drowing (1 case), and small-small intestinal invagination (1 case), three others developed acute bilateral large focal pneumonia with or without repeated atelectases. The drug Surfactant-BL was administered in a dose of 400 micrograms/m2 by instillations (2 cases) or by inhalation aerosols. The drug improved blood gases, lung compliance, x-ray picture, and clinical status of all patients, permitting a decrease in IMV/SIMV parameters within 12-48 h after the last administration and discontinuation of IMV/SIMV in 3 patients within 24 h after 1 or two administrations. Five children survived, 1 (with asphyxial drowning) died with brain edema and wedging syndrome. Surfactant-BL is a safe and effective drug; administration through alveolar nebulisers should be preferred.