A new compound, 9-chloro-5-oxo-7-(1H-tetrazol-5-yl)-5H-[1]-benzopyrano[2,3- b]pyridine sodium salt pentahydrate (traxanox sodium, Y-12141) has been shown to exert uricosuric effect in animal experiments. This study was performed to investigate the pharmacokinetics and pharmacological effects of this compound in healthy subjects by double-blind, cross-over comparison with placebo. The urine volume and urinary electrolytes increased significantly after single oral doses of 120 and 360 mg. Urinary excretion of uric acid tended to increase and serum uric acid decreased significantly. Traxanox sodium did not induce any significant change in blood pressure and pulse rate. These results suggest that traxanox sodium is a useful diuretic agent with uricosuric effect.