This study examined the prognostic value of the APACHE II scoring system in patients undergoing emergency operations for bleeding peptic ulcer. There were 96 operations for gastric ulcers and 58 for duodenal ulcers. The mean scores in survivors and in patients who died were 10.8 and 17.5 respectively. None of the 66 patients with an APACHE II score less than 11 died, while the mortality rate in those scored greater than 10 was 22 per cent. In patients scored greater than 10 non-resective procedures carried less risk of mortality than gastrectomy. The APACHE II score is useful when measuring the severity of the acute disease and predicting the outcome in these patients. If used in daily practice it may assist the surgeon in stratifying patients into a low-risk group (score less than 11) in which major operations are well tolerated and outcome is favourable and a high-risk group (score greater than 10) in which the risk of mortality is high and the performance of procedures of lesser magnitude is probably more likely to improve survival.