Abstract Postoperative chest infection occurred in 65 of 200 patients, 100 of whom had biliary disease and 100 duodenal ulcer. As might be expected the incidence of chest infection was significantly higher in males, in those with duodenal ulcer, in industrial workers and those with preoperative chest symptoms, particularly if they smoked. Contrary to what might be expected it was not significantly higher in smokers in general, obese patients and those having longer operations. Although the incidence is high in the 40–60 age group it is not directly related to age. There appears to be a seasonal variation.