?Objective To observe the apoptosis inducing effect of recombined human tumor necrosis factor alpha(rhTNF α) on human umbilical cord endothelial cells(HUCEs) and the antagonistic effect of Naotaifang extract(NTE) on it. Methods The cultured HUCEs were randomly divided into 6 groups,including blank controlling group (BCG),NTE controlling group(NCG)with mid dose NTE added only,rhTNF α group(TNG) with 100?ng?/ml rhTNF α added only and 3 treating groups(TG1～3) with various dosage of NTE(100?ng rhTNF α plus 6?mg?/ml,2?mg?/ml or 0.67?mg?/ml NTE) respectively. Then, the cells were cultured for 24?h and dyed with AO/EB thereafter for apoptotic cells counting under fluorescence microscope.Results Most cells were seen living cells with normal morphology in CG and NCG,with the rates of apoptosis being 14.0% and 14.5% respectively. The cells in TNG and TG3 were seen with much more typical apoptotic featunes and the rates of apoptosis were 75.0% and 63.3% for the two groups respectively.However,the cells in TG1 and TG2 were shown with fewer apoptotic features and the rates of apoptosis for these two groups were 43.5% and 53.0% respectively.Conclusion NTE is effective to antagonize the apoptosis inducing effect of rhTNF α on HUECs. 〔