Reactive oxygen species have been implicated in the pathogenesis of contrast-induced nephropathy (CIN). We investigated the relationship between CIN with paraoxonase 1 (PON-1) activity and oxidative stress markers (total antioxidant status [TAS], total oxidant status [TOS], and oxidative stress index [OSI]) in patients with anterior ST-segment elevation myocardial infarction (STEMI) undergoing primary percutaneous coronary intervention; 289 consecutive patients with STEMI were prospectively included. The patients were divided into 2 groups: CIN (n = 69) and non-CIN (n = 220). Activity of PON-1 and TAS levels were significantly lower and OSI and TOS levels were significantly higher in patients with CIN compared to the non-CIN group (P < .05, for all). On multivariate logistic regression analysis, PON-1 activity and OSI as well as the amount of contrast medium and diabetes were independent predictors for CIN in patients with anterior STEMI. Activity of PON-1 and oxidative stress may play a role in the pathogenesis of CIN.