Gallstone ileus is rare following an Endoscopic Retrograde Cholangio-Pancreaticography (ERCP). We present a case where gallstones caused ileus and perforation of small bowel after a therapeutic ERCP. There was no previous history of instrumentation of the papilla or a cholecystoenteric fistula. This case points out a serious morbidity of therapeutic ERCP for large common bile duct stones.