Objective To test whether pre-medication with pronase and lidocaine hydrochloride mu- cilage can reduce the procedure time and improve image visibility in endoscopic uhrasonography (EUS). Methods A total of 80 patients who accepted EUS were randomly assigned to group A to have oral lidocaine hydrochloride mucilage 10 ml 15 minutes before the examination or group B to have oral 10 000 unit pronase with 1 gram sodium bicarbonate plus warm water up to 50 m| 30 minutes before EUS and oral 10 ml lidocaine hydrochloride mucilage 15 minutes before the procedure. The total checking time, EUS image visibility scores ( range 1-4) were recorded. Results The operation time of group A ( 15.5 ± 3.0 minutes) was sig- nificantly longer than that of group B ( 12. 3 ±2. 3 minutes, P 〈0. 001 ). The EUS images from group B had higher visibility scores than group A (P 〈 0. 05). Conclusion Pre-medication with pronase and lidocaine hydrochloride mucilage can reduce the procedure time and improve image visibility in EUS. Key words: Endosonography; Pronase ; Lidocaine ; Image visibility