Adult respiratory distress syndrome, characterized by high permeability pulmonary oedema caused by endothelial cell damage, resulting in refractory hypoxemia, has a very high mortality. Cardiopulmonary bypass is said to be responsible for the development of adult respiratory distress syndrome after cardiac surgery. The present study was performed in order to identify predicting and aetiological factors of adult respiratory distress syndrome and multiple organ failure after cardiac surgery. Between January 1984 and December 1993, 3848 patients underwent cardiac surgery with cardiopulmonary bypass in the authors' institution, and were analysed in a retrospective manner. The operations performed were 3444 coronary artery bypass grafts (CABG), 267 valve and 137 combined (CABG + valve) procedures. The incidence of adult respiratory distress syndrome was 1.0% (38 of 3848) with an overall mortality rate of 68.4% (26 patients); 24 of these died from multiple organ failure. Multivariate regression analysis identified hypertension, current smoking, emergency surgery, preoperative New York Heart Association (NYHA) class 3 and 4, low postoperative cardiac output and left ventricular ejection fraction < 40% as significant, independent predictors for adult respiratory distress syndrome. Combined cardiac surgery and diffuse coronary disease were also significant predictors; cardiopulmonary bypass time was not. Thirty-six of the 38 patients that later developed adult respiratory distress syndrome had low postoperative cardiac output, 12 requiring intra-aortic balloon pump support. The remaining two had severe hypotension caused by postoperative bleeding. Twenty-six adult respiratory two had severe hypotension caused by postoperative bleeding. Twenty-six adult respiratory distress syndrome patients (68%) had confirmed gastrointestinal complication (e.g. intestinal ischaemia). Adult respiratory distress syndrome is a rare complication after cardiac surgery but is associated with a very high mortality. Preoperative predictors were identified. Cardiopulmonary bypass alone was not found to be an important factor. Postoperative low cardiac output leading to splanchnic hypoperfusion may be the most important single factor in developing adult respiratory distress syndrome after cardiac surgery.