Background: Early detection of renal impairment (RI), one of the major complications of liver cirrhosis, using the current markers and equations could be challenging. Serum cystatin C (CysC) was proposed as an effective reflection of the glomerular filtration rate (GFR). However, its role in patients with liver cirrhosis has not been extensively verified especially in the detection of early RI. Patients and Methods: Seventy consecutive potential candidates for living donor liver transplantation were included in this prospective study as they fulfilled: age 18-80 years, serum creatinine (Cr) <1.5 mg/dL and no dehydration, sepsis or GI bleeding during the month before enrollment. CysC, Cr and estimated GFR [creatinine clearance (CCr), Cockcroft-Gault formula (C-G) and MDRD equations with 4 and 6 variables] were all correlated to isotopic GFR. Early RI was defined as GFR of 60-89 mL/min/1.73 m2. Results: Patients included 61 (87.1%) males, and had a mean age of 47.4±9.3 years and mean body weight of 78.2±14.7 kg. Liver cirrhosis was mostly due to chronic viral hepatitis, HCV in 51 (72.9%) and HBV in 12 (17.1%) patients, and 20 (28.6%) patients had hepatocellular carcinoma. The mean MELD was 16.2 (range 8-31); 18 (25.7%) and 52 (74.3%) patients were Child-Pugh class B and C, respectively. GFR was ≥90, 60-89 and 30-59 mL/min/1.73 m2 in 22 (31.4%), 45 (64.3%), and 3 (4.3%) patients, respectively. The mean Cr was 0.8±0.3 mg/dL and mean CysC was 1.9±1 mg/L. The GFR (mL/min/1.73 m2) was measured isoto-pically as 84.5±16.6, and estimated as: C-G 132.9±65, CCr 82.4±31.3, MDRD4 119.2±63.5 and MDRD6 97.4±50.4. All markers and equations, except C-G (p=0.100), were significantly correlated to GFR: 1/CysC (r=0.437, p<0.0001), CCr (r=0.367, p=0.002), 1/Cr (r=0.287, p=0.016), MDRD4 (r=0.260, p=0.030) and MDRD6 (r=0.286, p=0.017). The table shows the area under the curve (AUC) for discriminating early RI. At a cutoff value of 1.2 mg/L, CysC was 89.6% sensitive and 63.6% specific in detecting early RI. Conclusion: In patients with liver cirrhosis, CysC showed the highest significant correlation to GFR and was the test that best discriminated early RI especially at a cutoff of 1.2 mg/L.