The effects of aldioxa and cetraxate hydrochloride on the formative process of gastritis induced with intragastric application of 2% sodium hydroxide were studied. Rats were given food including either aldioxa or cetraxate hydrochloride for 6 weeks after the sodium hydroxide application. After sacrifice, the stomachs were removed, and the gastric mucosa were observed macroscopically and histologically. Gastric mucosal injury was widely induced with sodium hydroxide, being histologically characterized by mucosal hypertrophy, cell infiltration and intestinal metaplasia. These lesions seem to be the early stage of chronic gastritis. The aldioxa group showed a decrease of mucosal hypertrophy and cell infiltration as compared with the control group. In the cetraxate hydrochloride group, the mucosal surface of white gray color and the mucosal bosselation were observed macroscopically. Histologically, these were found to be cell infiltration and cyst formation. Moreover, intestinal metaplasia occurred at high incidence in this group. These findings in the cetraxate hydrochloride group are recognized to be an aggravation of chronic gastritis. From the above results, it is suggested that aldioxa promotes good regeneration of mucosa and should be useful for the clinical therapy of chronic gastritis.