Plasma and urine oxypurines (hypoxanthine and xanthine) and uric acid, were evaluated in normal subjects and in gouty patients before and after a purine free diet. After a 7-days period, plasma oxypurines were remarkably higher in normal subjects, while they did not undergo variations in gouty patients, which showed higher in basal conditions. No significant changes in urinary excretion were observed in both cases. The interpretation of the observed variations is discussed.