We have studied 45 patients with postoperative adult respiratory distress syndrome (ARDS) who were treated by mechanical ventilation during the last four years. This period was divided into two periods, and the mortality and progress after treatment were analysed. The overall, mortality was 56%. In the first period this rate was as high as 76%, while in the second period this rate improved to 43%. This improvement in the second period was thought to have resulted from aggressive cardiorespiratory treatment and the diminution of infection. According to the course of ARDS after treatment, four types could be classified. Type 1 showed rapid improvement in respiratory function. Type 2 showed gradual improvement. Type 3 showed relapse of respiratory failure. Type 4 resisted mechanical ventilation. Patients of types 3 and 4 had extremely poor prognoses. Stricter management to avoid infection, specific treatment of multiple organ failure (which was seen frequently) seemed advantageous. High frequency positive pressure ventilation (HFPPV) may have some role in improving the respiratory function of the patients with ARDS.