Renal excretion of ascorbic, dehydroascorbic and diketogulonic acids in uremia and relevant loss in hemodialysis are measured in comparison with those in patients with uremic syndrome (prior to hemodialysis) and in healthy subjects (control). Renal elimination of ascorbic acid was higher while of dehydroascorbic acid lower vs control. Elimination of diketogulonic acid was similar to control. In a session of hemodialysis, the organism loses 132.0 +/- 13.6 mg of ascorbic, 132.0 +/- 10.0 mg of dehydroascorbic and 204.0 +/- 9.0 mg of diketogulonic acid. 48-hour urinary losses of the patients reached 8.4 +/- 1.4, 19.6 +/- 1.1, 75.6 +/- 1.5 mg, respectively. Compared to control, hemodialysis patients lose the above acids 24.3, 2.7 and 4.6 times more.