Aim: Our aim was to evaluate the role of oxidative stress in the cholestatic liver disease Materials and Methods: Twenty patients with extrahepatic cholestasis due to the choledocholithiasis and fifteen healthy subjects were enrolled in the study. We performed endoscopic retrograde cholangiopancreatography (ERCP) for all patients and cholestasis was treated by sphincterotomy and stone extraction. In the patients (before and after ERCP) and in the healthy subjects, the levels of erythrocyte malonyldialdehyde (MDA), glutathione peroxidase (GSH-Px) and CuZn superoxide dismutase (CuZn SOD) were measured. Results: The levels of MDA in patients with cholestasis before ERCP were found to be higher comparing to the other groups. The levels of GSH-Px in the patients before ERCP were found to be higher, comparing to the patient group after ERCP and the control group. The levels of CuZn SOD in the patient group before and after ERCP were higher than those of the control group. The levels in the patient group before ERCP were higher than the patient group after ERCP, but this was not statistically significant. Conclusions: Our results showed the increase in the oxidative stress and the significant alterations in the different part of the antioxidant system in extrahepatic cholestasis.