Backgrounds: Green tea has abundant catechin which does powerful antioxidant action. It is known that catechin activates eNOS through PI-3-kinase, c-AMP dependent PK, Akt-dependent pathway and improves endothelial functions. The number of EPCs and flow-mediated endothelium dependent vasodilation (FMD) is reduced in chronic renal failure (CRF). This present study was designed to investigate the effect of endothelial dysfunction, number of circulating EPCs and oxidative stress by green tea consumption in patients of CRF. Methods : In 41 patients of chronic kidney disease of stage 4-5, who were divided into catechin group consuming green tea (5 g/day for 1 month) and control group not consuming green tea. The FMD, number of EPCs isolated from peripheral blood, inflammatory markers (hsCRP and interleukin-10) and oxidative stress (concentration of NOx(NO2- , NO3-), cGMP, MDA assay) were determined at baseline and at 4 weeks after green tea consumption. Circulating EPCs were quantified by flow cytometry as CD34+KDR2+ cells and by acyl-low-density lipoprotein and fluorescein isotiocyanate-lectin double positive cells after culture for 7 days. Results : Clinical characteristics, laboratory findings, oxidative stress, and inflammatory markers were not significantly different between the baseline and at 4 weeks after green tea intake except for decreased IL-10 in catechin group (0.36짹 0.11 vs 0.31짹 0.09, p=0.04). Circulating EPCs by flow cytometry and cultured EPCs could not check at both groups before and after green tea consumption during 4 weeks. FMD was significantly improved after 4 weeks in catechin group (5.52짹 2.68% vs 8.38짹 3.55%, p = 0.002). FMD was not significantly changed in control group. NMD was not changed before and after green tea consumption in both catechin and control groups. Conclusions : A short-term green tea consumption induces a rapid improvement of FMD, but not improved inflammatory marker, oxidative stress, and circulating EPC levels.