Accumulating evidence suggested that increased oxidative stress (OxSt) as well as inflammation are risk factors for cardiovascular events in hemodialysis patients. The incremental effect of online haemodiafiltration (OL-HDF) on markers of microinflammation ,and OxSt is less clear. Besides, the relationship between protein-bind uremic toxin and microinflammation remains obscure. The aim of this study was to evaluate the effect volume replacement of on-line hemodiafiltration on proinflammatory peripheral monocytes (percentage of CD14+CD16+ cells), PAF, IL-6 and on the plasma level of several oxidative stress markers as well as several protein-bound uremic toxins such as p-cresol, indole sulfate etc. In a case controlled study, 30 patients on OL-HDF will be evaluated. The association between protein-bound uremic toxins such as p-cresol, indole sulfate etc and AST-120, a spherical adsorptive carbon preparation (Kremezin) will also being investigated.