To determine the effect of hyperuricemia and allopurinol therapy on renal functions in chronic kidney disease (CKD) stage 3-4, we studied 96 patients in stage 3-4 CKD (57% male, age 65.3 ± 12.4 years). The mean estimated glomerular filtration rate (GFR) was 44.62 ± 14.38 iriL/ min/1.73 m 2 . The study patients were divided into non-allopurinol users (n = 47) and those using allopurinol (n = 49) in the last 12 months. Serum uric acid (UA) and C-reactive protein levels decreased after allopurinol therapy (P = 0.00 and P = 0.04, respectively), but no change was observed in the control group during the study period. In the allopurinol group, the mean GFR increased 3.3 ±1.2 mL/min/1.73 m 2 /year, while it decreased 1.3 ± 0.6 mL/min/1.73 m 2 in the control group during the follow-up period (P = 0.04); the patients in the allopurinol group exhibited lower levels of serum potassium, serum low-density lipoprotein (LDL) and renal resistance index (RRI) (P-values were <0.05). The patients with stable renal functions or GFR change <10% (n = 25) at the end of 12 months had significantly lower LDL and RRI values and more allopurinol users than the group with decreasing GFR (74% vs. 48%, P <0.05). In the regression analysis, UA and RRI were found as independent variables (r 2 = 0.68, P <0.01; r 2 = 0.25, P <0.01) that affected loss of renal function. We conclude that our study suggests a role for allopurinol, an effective agent in lowering serum UA levels, as a reliable therapeutic option in controlling renal progression in pre-dialysis CKD patients.