Three 1,2-benzothiazine derivatives were synthesized, and their analgesic / anti-inflammatory efficacy and their effect s of gastric irritation were evaluated. Among the three compounds, 39 exhibited the most potent anlagesic action, but the effect was weaker than that of piroxicam. Nonetheless, the compound showed 4 times more potent analgesic action with less gastric damage than did ibuprofen. These compounds did not show anti-inflammatory effect at an oral dose of 5 mg/kg.