During a 3-year period 0.1% of all patients undergoing surgery and 0.3% of the patients submitted for trauma developed ARDS. The diagnosis was based on strict criteria. Mortality among the 42 patients was 45.2%. Abdominal sepsis was associated with high mortality, trauma with a much better prognosis. Swan-Ganz catheters were used in 81% of the patients. The measurements were characterized by high pulmonary vascular resistance and increased intrapulmonary shunting. However, the initial recordings showed only small differences between survivors and fatal cases as regards haemodynamics and blood gas parameters. Mortality was associated with low diuresis, heart failure, need of inotropic support and on age of over 50 years. The significance of invasive central monitoring is discussed.