The substantial risk of biliary surgery in patients with liver cirrhosis may be reduced by preoperative preparation but the problem of the unknown cirrhotic remains. We studied 18 patients found incidentally to have cirrhosis at surgery. The perioperative complications and the outcome in these patients was compared with 18 non-cirrhotic patients, computer matched for age and sex, undergoing the same operations. Mean blood loss at operation was 324 ml (SD 218.1 ml) in the cirrhotic group and 105 ml (SD 74.7 ml) in the control group (P < 0.01). The postoperative complication rate was 38% in cirrhotics, but zero in controls (P < 0.01). The length of hospital stay was significantly increased in the cirrhotic group (P < 0.01). There was no mortality in either group. The incidental finding of cirrhosis at biliary surgery is associated with increased peroperative bleeding and increased morbidity. There is no increase in mortality in such patients.