The 2 subjects were a diabetic male with renal hypouricemia and a healthy male with normouricemia. In these subjects, 200 mg of benzbromarone increased fractional uric acid clearance (FUa) and 3.0 g of pyrazinamide decreased FUa. However, pyrazinamide did not inhibit the uricosuric action of benzbromarone at all on the administration of 3.0 g of pyrazinamide together with 200 mg of benzbromarone. These results indicated that in these cases, the relative role of each component could not be determined on the basis of the hypothetical four-component model.