In order to evaluate the prevention effect of Sunkiwhajung-tang (SWT) which has been used as a traditional prescription for the treatment of digestive disease in Korea on the gastric ulcer induced by indomethacin in rats, the changes of number and size of ulcerative lesions, parietal, chief, Grimelius and Serotonin-positive cells in the peri-ulcerative tissues were detected with histological examinations of ulcerative and peri-ulcerative lesions after oral injections of SWT extracts (125, 250 and 500 mg/kg, respectively). SWT prevented to a great extent the expected indomethacin-induced elevation in hemorrhagic ulcerative lesions, the number and size of ulcerative lesions, and the number of parietal cell, chief cell, Grimelius-positive cells and Serotonin-positive cells in the peri-ulcerative lesions in a dose dependent manner. These results provide a story evidence that SWT produced an protective effect on gastric ulcer induced by indomethacin. Determination of the specific mechanisms involved in the protective effect of SWT on the gastric ulcer will require additional study.