EUS-FNA is the standard of care for diagnosing pancreatic masses. According to the operator's preference, EUS-FNA with suction or without suction technique has been used. To date, little is known about optimal number of to-and-fro motion during each needle pass. As usual 10-15 to-and-fro motions was used for EUS-FNA with suction technique. Theoretically, more number of to-and-fro motions may be required in EUS-FNA without suction. In this circumstance, the contamination of blood in specimen and possible adverse event may occur. To determine optimal number of to-and-fro motion in EUS-guided FNA for pancreatic masses in terms of with suction or without suction, this prospective single-blinded randomized trial was conducted.