Radiological procedures requiring intravascular administration of iodinated contrast media are becoming a common source of an iatrogenic disease known as contrast-induced nephropathy (CIN). The treatment of established CIN is limited to supportive measures and dialysis. Therefore, identifying high-risk patients is the first step to minimize the overall risk of CIN. The purpose of this review is to describe classic and possible risk markers of CIN according to the ultimate clinical research and developments. Original publications, review articles, papers from our personal library, and guidelines on CIN were reviewed. Terms used for PubMed and Medline searches were as follows: "contrast-induced nephropathy," "radio-contrast nephropathy," "contrast nephropathy," "contrast medium-induced nephropathy," "contrast media," and "risk factors." No restriction was placed on date of publication. Preexisting renal failure, especially when secondary to diabetic nephropathy, is the most important risk marker for CIN.