Aim To explore the effect of melatonin(MT) on the proliferation and apoptosis in endothelial progenitor cells(EPC) from patients with coronary artery disease in vitro. Methods Total mononuclear cells were isolated from patients with coronary artery disease in vitro by Ficoll density gradient centrifugation,then the cells were plated on fibronectin-coated culture dishes.After 7 days,the attached cells were treated by MT with different concentrations(0,0.5,1.0,2.0 mmol/L) for different hours(6,12,24,48 h).EPC were identified by demonstrating the expression of CD34,VEGFR-2 and CD133 under a laser scanning confocal microscope.MTT assay was used to detect the effect of MT on the proliferation ability of EPC.EPC adhesion assay was performed by replating it on fibronectin-coated dishes,and the adherent cells were then counted.EPC migration were assayed by modified Boyden chamber assay.Flow cytometry was used to detect cell apoptosis.The expressions of bcl-2 mRNA and protein were detected respectively by RT-PCR and western blot. Results After exposured to MT,the proliferation,adhesion and migration of EPC in MT group was higher,and the cell apoptosis rate was lower than that in control group in a dose-dependent and time-dependent manner(P<0.01).Expression of bcl-2 mRNA and protein of EPC in MT group was higher than that in control group(P<0.01). Conclusion MT promotes the proliferation,adhesion and migration of EPC and inhibits the cell apoptosis via upregulating bcl-2 expression.