OBJECTIVE: Hyperuricemia is known as a risk factor that causes and worsens kidney diseases through a variety of mechanisms. Recent animal studies reported that the correction of hyperuricemia improved the renal function, but there have been few human studies. This study examined whether a hypouricemic treatment affects the renal function in Korean patients with gout. METHODS: Two hundred sixty-seven gout patients who were prescribed uric acid lowering agents for more than 1 year were enrolled at the Division of Rheumatology in the National Health Insurance Corporation Ilsan Hospital and Yonsei University Severance Hospital from January 2005 to January 2010. The following were examined: the levels of serum uric acid and serum creatinine, the amount of 24-hour urine uric acid, glomerular filtration rate (GFR), and abdominal ultrasound findings at baseline and follow-up. RESULTS: Mean age of the study subjects was 54.4+/-13.9 years. Two hundred forty-seven patients were male and 20 patients were female. The mean treatment duration was 35.0+/-19.5 months. Among the 267 patients, 219 and 19 patients received monotherapy with allopurinol and benzbromarone respectively, and 29 patients received combination therapy with allopurinol and benzbromarone. After the treatment with uric acid lowering agents, the serum uric acid and creatinine levels decreased significantly (8.05+/-1.96 mg/dL vs 6.16+/-1.46 mg/dL, p<0.001, 1.25+/-0.46 mg/dL vs 1.18+/-0.42 mg/dL, p=0.001, respectively) and the GFR increased significantly (74.4+/-27.0 mL/min/1.73 m3 vs 80.2+/-31.6 mL/min/1.73 m3, p<0.001). CONCLUSION: Treatment with hypouricemic agents reduced the levels of serum uric acid and improved the renal function. These results suggest that a hypouricemic treatment might improve the kidney function in gout patients.