The ethanol extract of the rhizomes of Kaempferia marginata showed a potent inhibitory effect against lipopolysaccharide (LPS)-induced nitric oxide (NO) and tumor necrosis factor-alpha (TNF-alpha) release in RAW264.7 cells. Moreover, the partition with various organic solvents also inhibited NO production. One new pimarane-type diterpene, 1alpha-acetoxysandaracopimaradien-2alpha-ol (5), along with four known diterpenes (1-4), were isolated from the n-hexane and chloroform layers, respectively. Among these metabolites, compounds 1 and 4 were isolated for the first time from K. marginata. Compounds 1-5 showed significant inhibitory effects on NO production, with IC50 values ranging from 38.6 to 51.9 microM. Furthermore, compound 2 also exhibited significant activity against TNF-alpha release (IC50 = 48.3 microM). These findings may support the use of K. marginata by traditional doctors for treatment of inflammatory-related diseases.