Detailed studies have been made of the X-ray, endoscopic, and biopsy findings in 160 Japanese patients with acute gastritis. We classified these patients clinically into three types: type I, edematous; type II, hemorrhagic; and type III, ulcerous type, on the basis of X-ray, endoscopic and biopsy findings. Type I is the mildest and seems to be completely cured within 1 week; however, type III requires a longer time to heal.