Recent epidemiological studies provide a clear evidence that hyperuricemia is associated with hypertension, coronary heart disease, left ventricular hypertrophy and progression of renal disease. Aim of our study was to assess the effect of low dosage of recombinant urate oxidase on hyperuricemia in renal failure patients that already receiving allopurinol. Our study group consisted of 43 renal failure patients, 23 women and 20 men. The mean age was 74 years (range 36-90 years). The following variables were studied on admission: serum creatinine, blood urea nitrogen and serum uric acid. Intravenous rasburicase was administered at a dose of 0.02 mg/kg/day on 3 consecutive days in patients with serum uric acid between 8-10 mg/dl, on 5 consecutive days in patients with serum uric acid between 10-15 mg/dl and on 7 consecutive days in patients with serum uric acid > 15 mg/dl. Uric acid levels were assayed after 48 hours and 7 days after rasburicase treatment. Mean values of uric acid levels after 48 hours were 2.47 mg/dl (+/- 1.58) in men and 2.77 mg/dl (+/- 2.24) in woman, where'as mean values of uric acid levels after 7 days were 4.45 mg/dl (+/- 2.0) in men and 5.75 mg/dl (+/- 1.9) in woman. No significant relationship were found between uric acid and creatinine as before as well after therapy. There were no side effects in all patients included in the study. After 7 days, the rasburicase therapy showed more antihyperuricemic effect in men (59%) than in women (46%).