Contrast induced nephropathy (CIN) is of great concern when using contrast media in the new era of medicine. CIN is defined as 25-50% relative increase, 0.5-1 absolute increase in serum creatinin value or 25% fall in GFR. The incidence of CIN is found to be 0% to 10% in general population and up to 50% in high risk population. High risk patients include those with chronic kidney disease (GFR<60 ml/min/1.73 m²) Diabetes Mellitus, congestive heart failure, anemia and advanced age. Amount and kind of contrast medium and decreased circulating blood volume are other important predictors of CIN. 50% of cases of CIN happen within 24 hours of contrast injection. Maximum creatinin levels are reached between 48-72 hours. It usually returns to previous levels in 7-10 days. Suggested mechanisms are renal vasoconstriction and tubular injury. N-acetylcysteine and hydration are proved to be protective against CIN and theophylline may have a role. In this study, it is hypothesized that pentoxifylline, a dimethylxanthine, can also protect renal cells from CIN. It has been observed that pentoxifylline improves oxygen delivery to ischemic tissues, diminishes oxidative damage to renal tissue and may also scavenge free radicals. Percutaneous coronary intervention is assumed a high risk procedure for developing CIN as the amount of contrast used in PCI is remarkable. Therefore, the patients undergoing PCI were selected for the trial. A prospective randomized trial will be conducted on patients undergoing PCI.