Aim To investigate the effect of simvastatin on CD40 expression induced by tumor necrosis factor α (TNF α) and interferon γ (IFN γ). Methods Human umbilical vein endothelial cells (hUVECs) cell line (ECV 304) were cultured with simvastatin (0～10 μmol/L) , and stimulated with 100 kU/L TNF α and 1 500 kU/L IFN γ. We detected CD40 expression levels in hUVECs by reverse transcription polymerase chain reaction (RT PCR) and flow cytometry (FCM) analysis. Results In ECV 304, exposure to TNF α (100 kU/L) plus IFN γ (1 500 kU/L) resulted in a marked increase in CD40 expression; CD40 mRNA expression reached a maximum at 9 h, and protein at 20 h. Simvastatin attenuated the expression of CD40 exposed to TNF α (100 kU/L) plus IFN γ (1 500 kU/L) in a dose dependent manner, with a maximal effect at concentration of 10 μmol/L. On mRNA level, relative intensity quantification compared with basal were 90.9%±38.8% vs 228.0%±49.6% (p<0.05); on protein level, CD40 + cells ratio were 20.1%±1.3% vs 54.1%±6.1%(p<0.05). Conclusions Simvastatin can inhibit CD40 expression induced by TNF α/IFN γ. These results may have important implications for mechanism of anti inflammatory and immunological effect of statins.