This study examnined the effects of tanshinone derivatives (tanshinone I, cryptotanshinone, 15,16-dihydrotanshinone I) on prostaglandin (PG) and nitric oxide (NO) metabolism in an attempt to establish their anti-inflammatory mechanisms and to present a scientific rationale for the use of Salvia miltiorrhiza (danshen) in inflammatory conditions. From lipopolysaccharidetreated RAW 264.7 cells, cyclooxygenase-2 (COX-2)-mediated $PGE_2$ production was inhibited by tanshinone I, cryptotanshinone and 15,16-dihydrotanshinone I, while only cryptotanshinone and 15,16-dihydrotanshinone I inhibited inducible NO synthase (iNOS)-mediated NO synthesis at $1-50;{mu}M$. Particularly, cryptotanshinone was found to be a down-regulator of proinflammatory molecule expression, including COX-2 and iNOS. The electrophoretic mobility shift assay showed that cryptotanshinone and 15,16-dihydrotanshinone I also inhibited the activation of the transcription factors, such as nuclear transcription factor-${kappa}B$ and activator protein-1. Moreover, cryptotanshinone exhibited in vivo anti-inflammatory activity against carrageenaninduced paw edema in rats. Overall, these results provide additional scientific rationale for the anti-inflammatory use of danshen in Chinese medicine. Especially, cryptotanshinone and 15,16-dihydrotanshinone I are important constituents.