Patients with Gilbert's syndrome suffer from an abnormality which makes them jaundiced from time to time. A number also develop gallstones and come to cholecystectomy. If this condition has not been recognized these patients may subsequently run the risk of unnecessary operations on their bile ducts from the mistaken assumption that the intermittent episodes of jaundice which are a feature of the syndrome are due to a stone which has been left behind. Such a case history is reported here.In an attempt to determine how frequently these conditions coexist a prospective study was carried out on patients about to undergo cholecystectomy for stones in the gallbladder. Gilbert's disease was found to be present in 2 of 67 males (3.2% +/- 0.8%) but not in 184 females. Hence it seems that about 1 in every 30 males subjected to cholecystectomy may be expected to have this abnormality.It is suggested that this places an obligation on the clinician to have liver function tests done on at least two occasions preoperatively in male patients with cholelithiasis in an attempt to detect this abnormality and avoid this surgical pitfall.