In a series of 204 patients with common duct stones, sphincterotomy was not possible in 10, due to an impacted stone in the papilla. An endoscopic choledocho-duodenostomy was performed which was effective in all cases. One patient suffered a retroperitoneal perforation which was managed medically. This technique is an effective alternative to sphincterotomy in the treatment of impacted papillary stones. Retroperitoneal perforation is a major risk to be taken into account.