Background This study analyzed the impact of chronic renal insufficiency (CRI) on early and late clinical outcomes of carotid artery stenting (CAS) using serum creatinine and glomerular filtration rate (GFR). Study Design There were 313 CAS patients classified into 3 groups: normal (serum creatinine <1.5 mg/dL or GFR ≥ 60 mL/min/1.73 m2); moderate CRI, and severe CRI (serum creatinine ≥3 or GFR < 30 mL/min/1.73 m2). Major adverse events ([MAE] stroke, death, and myocardial infarction) were compared for all groups. Results Using serum creatinine, perioperative stroke rates for normal, moderate, and severe CRI were: 5%, 0%, and 25%, respectively, (p = 0.05) vs 4.6%, 3.7%, and 11.1%, respectively, (p = 0.44) using GFR. The perioperative MAE rates for symptomatic patients were 9.3% and 0% (p = 0.355) and 2% and 5.9% (p = 0.223) for asymptomatic patients for normal and moderate/severe CRI, respectively, using serum creatinine vs 8.1% and 7.8%, respectively, for symptomatic patients and 2.5% and 3%, respectively, for asymptomatic patients using GFR. At a mean follow-up of 21 months, late MAE rates in normal vs moderate/severe CRI patients were 8.2% and 14%, respectively, (p = 0.247) using serum creatinine vs 6.6% and 13.3%, respectively, (p = 0.05) using GFR. Late MAE rates for symptomatic patients in normal vs moderate/severe CRI were: 8.7% vs 27%, respectively, (p = 0.061) using serum creatinine and 5.7% vs 18.8%, respectively, (p = 0.026) using GFR. Late death rate was 0.55% in normal vs 7.6% (p = 0.002) for moderate/severe CRI. Freedom from MAE at 3 years in symptomatic patients was 81% in normal and 46% in moderate/severe CRI (p = 0.0198). A multivariate Cox regression analysis showed that a GFR of < 60 mL/min/1.73 m2 had an odds ratio of 1.6 (p = 0.222) of having a MAE after CAS. Conclusions The GFR was more sensitive in detecting late MAE after CAS. Carotid artery stenting in moderate CRI patients can be done with a satisfactory perioperative outcome; however, late death was significant.