In rats, administration of Casearia sylvestris extract derived from fresh and dried leaves protects stomach mucosa without changing gastric pH. In stress-induced acute lesions, the preventive effect of extract from dried leaves is more effective than extract from fresh leaves. In acetic acid-induced chronic ulcer, both extracts reduce the size of ulceration and increase the number of collagen fibers after 5 days of treatment, and these effects are similar with both extracts. These antiulcer activities of Casearia sylvestris may be due to the presence of volatile oils, tannins and triterpenerelated compounds.