Chronic kidney disease (CKD) is a frequent complication of diabetes mellitus. However, the role of CKD in outcomes of patients with diabetes who have undergone percutaneous coronary intervention (PCI) has not been studied specifically. Therefore, we investigated the impact of CKD on prognosis of patients with diabetes who underwent PCI. Of 1,575 diabetic patients who underwent PCI, 1,046 (66%) had preserved renal function, 492 (31%) had CKD (baseline serum creatinine >1.5 mg/dl or estimated glomerular filtration rate <60 ml/min/1.73 m(2)) without dialysis, and 37 (2.3%) were dependent on dialysis. Patients with CKD versus those without CKD had more in-hospital complications, including mortality (2.6% vs 0.5%, respectively; p <0.0001), neurologic events (3.1% vs 0.6%, p = 0.0001), and gastrointestinal bleeding (2.9% vs 0.9%, p = 0.01). Contrast-induced nephropathy after PCI (increase > or =25% and/or > or =0.5 mg/dl of serum creatinine before PCI vs 48 hours after PCI) was found in 15% of patients without CKD versus 27% of those with CKD, and de novo dialysis was instituted in 0.1% versus 3.1%, respectively. Contrast-induced nephropathy was independently predicted (all p <0.0001) by peri-PCI hypotension (odds ratio [OR] 2.62), insulin treatment (OR 1.84), and volume of contrast medium (OR 1.30). The 1-year mortality rate was strikingly higher (all p <0.0001) in patients with CKD who did not receive dialysis (16%) and those on dialysis (44%) compared with the group with preserved renal function (5%). Contrast-induced nephropathy was among the independent predictors of a 1-year mortality rate (OR 2.75, p <0.001).