For diagnosis of pancreatic tumors, endoscopic ultrasound (EUS) and EUS-guided fine needle aspiration (EUS-FNA) are well established techniques in clinical practice. In the case of EUS, an ultrasonic transducer located at the tip of the echoendoscope allows the endoscopist to visualize the wall of gastrointestinal tract as a series of definable layers corresponding to histology, and also enables detailed images of areas outside of the digestive tract. EUS has a significant clinical impact because it allows assessment of submucosal GI lesions, loco-regional staging of gastrointestinal malignancy, tissue diagnosis by EUS-FNA and staging of pancreaticobiliary lesions, non-small-cell lung carcinoma, and mediastinal disease. In prospective trials, EUS-FNA has been clearly established to be an important diagnostic tool with excellent safety profile.