In normal persons and gouty subjects, allopurinol is mainly converted to oxypurinol by xanthine oxidase and oxypurinol is then excreted unchanged by the kidney1. The concentration of serum oxypurinol is directly related to the renal clearance of oxypurinol2, which is increased or decreased under various conditions2, 3. While the renal handling of oxypurinol seems to be similar to that of uric acid 2, 4, the renal transport mechanism(s) of oxypurinol has not yet been clearly elucidated. Therefore, in this work we studied the renal handling of oxypurinol together with oxypurines using uricosuric agents (probenecid and benzbromarone) and pyrazinamide which affect the renal transport of uric acid.