The inhibitory effects of 2,3,5,4'-tetrahydroxystilbene-2-O-beta-d-glucoside (THSG), extracted from the roots of Polygonum multiflorum Thunb, on inflammatory activity in animal models and cyclooxygenase-2 (COX-2) activity in lipopolysaccharide (LPS)-induced mouse RAW264.7 macrophage cells were investigated. The carrageenin (CGN)-induced rat paw oedema model and dimethylbenzene-induced mouse ear oedema model were prepared; MTT assay, semi-quantitative RT-PCR, Western blot and ELISA were adopted. THSG 2.3, 4.6 and 9.2 mg kg(- 1) by oral administration inhibited mouse ear oedema and the percentage of inhibition of THSG 9.2 mg kg(- 1) is 87%. THSG 3.2, 6.4 and 12.8 mg kg(- 1) by oral administration dose-dependently inhibited rat paw oedema and the percentage of inhibition of THSG 12.8 mg kg(- 1) is 56% at 6 h. Indomethacin 13 and 9 mg kg(- 1) showed 90% and 57% inhibition in the same animal models, respectively. LPS 1 microg ml(- 1) significantly up-regulated prostaglandin E(2) (PGE(2)) production (inducing COX-2 activity) by 35% (exogenous arachidonic acid, AA), which was dose-dependently decreased by THSG 1, 10, and 100 micromol L(- 1) and the percentage of inhibition of THSG 10 micromol L(- 1) was 40%. NS-398 10 micromol L(- 1) decreased PGE(2) production by 42%. THSG 1, 10, 100 micromol L(- 1) was shown to markedly inhibit the LPS-induced COX-2 protein and mRNA expression in RAW264.7 cells (P < 0.05) but had no effect on COX-1 protein and mRNA (P>0.05). In summary, the data showed that THSG possessed an anti-inflammatory effect, which was perhaps related to the inhibition of COX-2 enzyme activity and expression in RAW264.7 macrophage cells.