Intestinal malrotation is a rare disorder typically beginning in childhood. In the adult it is an uncommon diagnosis, and it usually begins with bowel obstruction. It is a congenital anomaly only once reported to be associated with other gastrointestinal abnormalities in an adult. We reviewed all patients with intestinal malrotation at the Johns Hopkins Hospital during the past 7 years to determine the incidence of associated biliary tract anomalies. Eight adult patients were found to have complete malrotation of the gut. Four patients (50%) had an associated abnormality of the biliary tree. Two of four patients had a clinical presentation consistent with biliary tract disease rather than intestinal malrotation. Two patients underwent exploration; the gallbladder was found to arise from the left lobe of the liver. Two patients underwent exploration; in these patients the porta hepatic structures were anterior to the duodenum (complete anteroposterior portal hepatic malrotation). None of the biliary abnormalities were suspected before surgery. Malrotation was diagnosed before operation in only two of the eight patients. We conclude that intestinal malrotation is rare in the adult, and it can be associated with biliary tract anomalies or disease. In an adult with suspected intestinal malrotation and biliary tract disease, the surgeon should be aware of possible variable or abnormal extrahepatic choledochal anatomy.