In this thesis, the incidence of contrast-induced nephropathy (CIN) in diabetic patients undergoing percutaneous coronary intervention has been studied. Two types of dyes were used, the 1st is ionic-high osmolar dye and the 2nd is nonionic-low osmolar dye. Risk factors for CIN have been evaluated such as DM, hypertension, preexisting renal disease, anemia, and gender. Evaluation of the use of n-acetylcysteine as a measure to decrease the incidence of CIN has also been done. The most important risk factors were preexisting renal disease, DM and anemia. Neither nonionic - iow osmolar contrast media nor n-acetylcysteine was a satisfactory protective measure against CIN