The fruits of Gardenia jasminoides Ellis have been previously reported to possess anti-inflammatory activity. In this study, the constituents including geniposide, geniposidic acid, genipin and crocin were evaluated for their effects on prostaglandin and NO production in an attempt to establish anti-inflammatory cellular mechanisms. Among the constituents tested, only genipin significantly inhibited cyclooxygenase-2-mediated $PGE_2$ and inducible nitric oxide synthase-mediated NO production from lipopolysaccharide-treated RAW 264.7 cells at 10-100 ${mu}$M. Genipin also inhibited nuclear transcription factor-${kappa}B$ activation. Moreover, genipin showed in vivo antiinflammatory activity on ${lambda}$-carrageenan-induced paw edema in mice (10.4-29.9% inhibition at 20-100 mg/kg, i.p.). All of these results suggest that genipin may contribute to anti-inflammatory activity of the fruits of G. jasminoides and an inhibitory action on prostaglandin and NO production is, at least, the part of anti-inflammatory mechanism of genipin.