Chronic kidney disease (CKD) is gradually recognized as an independent risk factor for cardiovascular and cardio-/cerebrovascular disease. This study aimed to examine the association of the estimated glomerular filtration rate (eGFR) and clinical outcomes at 3 months after the onset of ischemic stroke in a hospitalized Chinese population. Totally, 972 patients with acute ischemic stroke were enrolled into this study. Modified of Diet in Renal Disease (MDRD) equations were used to calculate eGFR and define CKD. The site and degree of the stenosis were examined. Patients were followed-up for 3 months. Endpoint events included all-cause death and newly ischemic events. The multivariate logistic model was used to determine the association between renal dysfunction and patients' outcomes. Of all patients, 130 patients (13.4%) had reduced eGFR (<60mL/min/1.73m(2)), and 556 patients had a normal eGFR (>= 90mL/min/1.73m(2)). A total of 694 patients suffered from cerebral artery stenosis, in which 293 patients only had intracranial artery stenosis (ICAS), 110 only with extracranial carotid atherosclerotic stenosis (ECAS), and 301 with both ICAS and ECAS. The patients with eGFR <60mL/min/1.73m(2) had a higher proportion of death and newly ischemic events compared with those with a relatively normal eGFR. Multivariate analysis revealed that a baseline eGFR <60mL/min/1.73m(2) increased the risk of mortality by 3.089-fold and newly ischemic events by 4.067-fold. In further analysis, a reduced eGFR was associated with increased rates of mortality and newly events both in ICAS patients and ECAS patients. However, only an increased risk of newly events was found as the degree of renal function deteriorated in ICAS patients (odds ratio=8.169, 95% confidence interval=2.445-14.127). A low baseline eGFR predicted a high mortality and newly ischemic events at 3 months in ischemic stroke patients. A low baseline eGFR was also a strong independent predictor for newly ischemic events in ICAS patients. Abbreviations: BMI = body mass index, CKD = chronic kidney disease, CTA = computed tomographic angiography, ECAS = extracranial carotid atherosclerotic stenosis, eGFR = estimated glomerular filtration rate, ICAS = intracranial artery stenosis, MDRD = Modification of Diet in Renal Disease, MRA = magnetic resonance angiography, NIHSS = National Institute of Health stroke scale.