Endoscopic ultrasonography (EUS) is an essential technique required in diagnosis of pancreatobiliary diseases. In previous studies, 6% of patients who undergone EUS had significant throat pain. (NRS scale 5 or greater) Although some endoscopists think balloon inflation while EUS insertion could result in decreased throat damage and pain, there is no data to back up. We designed a single center randomized pilot study to compare throat pain caused by EUS insertion with conventional vs balloon inflation method.