Abstract: Objective To investigate the mechanisms for the cytopathic effect(CPE) of human cytomegalovirus(HCMV) in ECV304 endothelial-like cells.Methods PCR and indirect immunofluorescence were used to detect HCMV infection by examining immediate-early(IE) gene and protein expression of the virus in ECV304 cells.Phase-contrast and electron microscopies were performed to observe the morphological changes of the infected and uninfected cells,and DNA ladder analysis and flow cytometry were carried out to study HCMV-induced cell apoptosis.Results In HCMV-infected ECV304 cells,cytopathic effects were first observed at approximately 72 h post-infection.The cells with CPE changes exhibited detachment from the monolayer,cell rounding and shrinkage.The expression of the IE gene was detected.Chromatin condensation and nuclear fragmentation along with dramatic changes of the mitochondria were observed by electron microscopy at 96 h post-infection.Cellular DNA fragmentation was observed in the infected cells,which had cells apoptotic rates of 4.1% and 45.7% at 96 h and 144 h post-infection,respectively.Conclusion HCMV can induce apoptosis of ECV304 endothelial-like cells