Broncho-alveolar lavage fluid was obtained from a 24 yr old man who developed the adult respiratory distress syndrome 1 day after massive trauma and hemorrhagic shock. The lungs were available 3 days later when organ transplantation was performed. When the various fractions of the lavage material obtained by centrifugation, including the purified surface-active lipid-protein aggregates, were examined on the film balance, they revealed the usual minimal surface tension of 16-18 dyn/cm at 37.degree. C but the compressibility of the films from the lungs with adult respiratory distress syndrome was 5-10 times higher than the normal range. This suggests that surfactant films in the adult respiratory distress syndrome are less responsive to stress, and that as a result, a loss of film elasticity may contribute to the abnormal pressure-volume relationships observed with the intact lung. Changes in the lipid-to-protein ratios of the purified lipid-protein aggregates were found, as indicated by the recovery of 3 lipid-protein aggregates with different isopycnic densities from the lung with adult respiratory distress syndrome; only 1 major aggregate could be recovered from the lavages of normal lungs.