Value of endoscopic ultrasonography in diagnozing the pancreatic head mass LI Zhao-shen, ZHAN Xian-bao.Department of Gastroenterology,Changhai Hospital, the Second Military Medical University,Shanghai 200433，China Corresponding author: LI Zhao-Shen, E-mail：zhsli1956@hotmail.com Abstract Common etiologies of pancreatic head mass include carcinoma,cystic lesions,inflammatory lesions and neuroendocrine tumours,etc. The value of traditional imaging modalities in diagnozing pancreatic head mass is limited. Using high frequency and short distance scanning techniqes, endoscopic ultrasound (EUS) can show the details of the mass. And also EUS-guided fine needle aspirations can acquire the specimen and establish pathological and cytologic diagnosis. Presently,EUS is prior to other imaging modalities in early diagnosis and preoperative evaluation of pancreatic carcinoma. There are special EUS features for chronic pancreatitis mass, autoimmune pancreatitis mass and cystic mass. EUS can also localize the pancreatic endocrine tumours accurately and acquire specimen preoperatively. A large amount of evidence confirmed that EUS had high accuracy and specificity in diagnozing pancreatic head mass.