Broncho-alveolar lavage fluid was obtained from a 24-year-old man who developed the adult respiratory distress syndrome one 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 to 18 dyne per cm at 37 degrees C, but the compressibility of the films from the lungs with adult respiratory distress syndrome was 5 to 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 also found, as indicated by the recovery of 3 lipid-protein aggregates with different isopycnic densities from the lung with adult respiratory distress syndrome; only one major aggregate could be recovered from the lavages of normal lungs.