Purpose: While even modest increases in serum creatinine (SCr) have been associated with an increase in in-hospital and long-term mortality, a pathophysiological link between the two is still unknown. The purpose of this study is to address whether contrast induced nephropathy (CIN) has influences on long-term renal function and to find a new definition of CIN. Methods: Database from two prospective studies on CIN after coronary catheterization, RECOVER and PROMISS, was reviewed. We identified patients who had records of SCr values till six months after the procedure. Creatinine clearance (CCr) was calculated by Cockroft-Gault equation. If available, SCr levels of six months before the procedure were also analyzed. Results: SCr and CCr changes of 253 patients were analyzed. Patients were classified according to peak increment in SCr within 48hr after procedure and baseline CCr. The change in CCr during 6 month follow-up was significantly lower in patients whose increment in SCr was 0.2mg/dL or more than in those whose increment in SCr was less than 0.2mg/dL(-6.00[SD 8.40] vs. 0.96[6.28] mL/min per 1.73m2, p<0.001). The same findings were shown even when the patients were classified according to baseline CCr (Table). In patients whose increment in SCr was 0.2mg/dL or more, there was an acceleration of CCr decrement after CAG (CCr change before CAG:0.04[0.48], after CAG:-1.05[0.97] mL/min per 1.73m2 per month, p=0.001). Conclusion: CIN may influence long-term renal function and this finding is a potential evidence to explain the poor prognosis of patients with CIN. Considering our study results, new definition of CIN- 0.2mg/dL increase in SCr- may be needed.