Abstract: AIM To study the effects of isorhapotigenin (Iso) on interleukin-8 (IL-8) production and mRNA expression in normal human synovial cells (HSC) induced with TNFα. METHODS IL-8 were assayed with RIA method. The mRNA expression of IL-8 was detected by RT-PCR method. RESULTS It was shown that TNFα at concentrations of 0.05 to 0.5 U·mL^-1 for 24 h significantly increased IL-8 production. The expression of IL-8 mRNA was also promoted by TNFα (0.5 U·mL^-1) for 6 h. Iso at the concentrations of 1×10^-6mol·L^-1 to 1×10^-5mol·L^-1 showed inhibitory effects on IL-8 production induced with TNFα (0.25 U·mL^-1). The further study indicated that Iso at the concentrations of 1×10^-6mol·L^-1 to 1×10^-5mol·L^-1 inhibited IL-8 mRNA expression in HSC induced with TNFα (0.25 U·mL^-1). CONCLUSION TNFα promoted IL-8 production and mRNA expression in HSC. Iso inhibited IL-8 production and mRNA expression induced by TNFα (0.25 U·mL^-1). This might be one of the anti inflammatory mechanisms of Iso.