The structure of a new triterpene derivative isolated from Poria cocos was determined to be 3 beta-p-hydroxybenzoyldehydrotumulosic acid by spectral and chemical methods. 3 beta-p-hydroxybenzoyldehydrotumulosic acid showed marked inhibitory activity against 12-O-tetradecanoylphorbol-13-acetate (TPA)- and arachidonic acid (AA)-induced ear inflammation in mice. The 50% inhibitory doses of 3 beta-p-hydroxybenzoyldehydrotumulosic acid were 0.27 and 1.25 mg per ear on TPA- and AA-induced inflammation, respectively.