Objective To explore the relationship bewteen serum cystatin C (Cys-C )and glomerular filtration rate(GFR) in creatinine-blind range elderly patients. Methods From Jan.2002 to Dec.2003,in the Affiliated Hospital of Luzhou Medical College,the study was performed in 86 elderly patients with chronic renal disease.Serum Cys-C was determined by particle-enhanced immunoturbidimetry.Serum creatinine(Scr) was determined by auto-analyzer.Creatinine clearance rate(Ccr) was estimated by CockCroft-Cault formula.For statistical evaluation,linear regression analysis was used. Results Concentration of Cys-C increased in 56 patients(56.1%).When Ccr was higher than 59mL/min,concentration of Cys-C increased in 44.2% patients.Significant positive correlation was observed between Cys-C and Scr( r =0.89, P