In this study, we aimed to investigate the condition of oxidative stress and antioxidative defence system in chronic hemodialysis patients. So, the malondialdehyde (MAD) levels, as the marker of lipid peroxidation, and the activities of glutathione peroxidase (GPx), catalase and superoxide dismutase (SOD) being components of enzymatic anticxidative defence system were measured in 20 patients, mean age 49,4±14.Iyears with chronic hemodialysis and 16 healthy volunteers, mean age 45,0±l 1.4 years. Both erythrocyte and plasma MDA levels of the hemodialysis patients were found to be increased compared to the control group (p<0.0001). GPx and SOD enzyme activity were lower in hemodialysis patients group compared to the control group (p<0.000 land p<0.0001, respectively) and catalase enzyme activity was higher in the group of hemodialysis patients compared to the control group (p<0.0001). In hemodialysis patients groups, both erythrocyte and plasma MDA level was lower after the dialysis compared to the level before hemodialysis and GPx and enzyme activity were found to be high after hemodialysis compared to the level before hemodialysis, (p<0.0001, p<0.05 and p<0.05, respectively). We could find no difference in SOD enzyme activity before and after hemodialysis (p>0.05). It was concluded as a result of this study that LP was high in hemodialysis patients compared to healthy subjects ant that hemodialysis treatment reduced oxidative stress.