We report a case of a 65-year-old man with a history of duodenal ulcer that treated preoperatively with ranitidine and underwent surgical exploration for upper gastrointestinal hemorrhage under emergency conditions. Under general anaesthesia, he showed resistance to two nondepolarizing neuromuscular blocking drugs. No obvious cause for the resistance was demonstrated except for the possibility of an interaction between ranitidine with vecuronium and mivacurium. ©2007, Fırat Üniversitesi, Tıp Fakültesi