Clear visualization of the gastrointestinal mucosal surface is essential for thorough endoscopy. An unobstructed assessment can reduce the need for additional timeconsuming manipulations such as frequent washing and suction, which tend to prolong total procedure time.However, mucus, foam, and bubbles often hinder clear visibility during endoscopy. Premedication with pronase,a compound of mixed proteolytic enzymes, has been studied in order to improve mucosal visibility during endoscopy. Although its effects differ according to the location in the stomach, premedication with pronase 10 to 20 min before endoscopy significantly improves mucosal visibility without affecting the accuracy of Helicobacter pylori identification. The effects of pronase as premedication also extend to chromoendoscopy,narrow-band imaging, magnifying endoscopy, and endoscopic ultrasonography. In addition, endoscopic flushing with pronase during endoscopy may improve the quantity and the quality of a biopsy to some degree.Although improved mucosal visibility does not necessarily improve clinical outcomes, premedication with pronase may be helpful for increasing the detection rate of early cancers.