The possibility of the practical use of endoscopic ultrasound (EUS)-guided puncture technique was examined. The aim of this study was to establish the safety and reliability of fine needle aspiration biopsy (FNAB) via gastrointestinal lumen under realtime ultra-sound guidance. All studies were performed with Toshiba-Machida echoendoscope EPE-703FL (7.5 MHz) and EPB-503 FS (5 MHz) with linear transducers. The results were as follows; 1) EUS-guided puncture and FNAB was performed with a modified EIS needle gauge 23, 20 mm in length set up on the EUS fiber with the rising device. 2) A transesophageal puncture model was made and several lymph nodes resected from an adult mongrel dog embedded in an agar. The tissue material obtained from EUS-guided FNAB was satisfactory for cytological examination. 3) EUS-guided transesophageal puncture was performed in 2 dogs under general anesthesia with no complications. We conclude that EUS-guided puncture technique was expected to be a new diagnostic procedure.