Background: Renal dysfunction is one of the common and major complications in liver cirrhosis with poor prognosis. Aim: To study the role of` serum creatinine and creatinine clearance in assessing renal function in patients with liver cirrhosis and to study the advantages of measuring the creatinine clearance by timed urine collection over creatinine clearance measured by Cockcroft-Gault formula. Materials and Methods: All adult patients of both sexes diagnosed to have liver cirrhosis were included in the study. Liver function test, renal function tests, 24-h urine volume, and urine creatinine were done. Creatinine clearance was calculated using the formula urine creatinine/serum creatinine multiplied by 24-h urine volume and also by the Cockcroft-Gault formula. Comparison between serum creatinine and creatinine clearance calculated by these two methods were done. Results: Of the 43 patients included in the study, 35 were male while remaining 8 were female. Mean blood urea and serum creatinine were 22.42 mg/dl and 1.01 mg/dl. 10 patients had a creatinine clearance of < 30 ml/min based on timed urine collection. Measurement of creatinine clearance using the Cockcroft-Gault formula showed significantly higher values when compared to that measured using timed urine collection. Ascites was present in 38 out of the 43 patients. Kidney size and corticomedullary differentiation were normal in all patients. Conclusion: Creatinine clearance should be done routinely in advanced liver disease to assess renal reserve. Creatinine clearance by timed urine collection has a strong predictive value when compared to creatinine clearance done using by Cockcroft-Gault formula.