The unripe fruit extract of Juglans mandshurica showed significant inhibition on aspirin and indomethacin induced gastric lesion at an oral dose of 1000 ㎎/㎏. The extract did not show inhibition of aspirin induced ulcer and Shay ulcer at the doses of 500 and 1000 ㎎/㎏. The results indicate that the extract had a gastroprotective activity.