Three trials were conducted to determine the changes in plasma ascorbic acid (AA) associated with varying levels and duration of supplemental AA. In Trial 1, supplemental AA was provided in the drinking water at 0, 5, 25, 50, 100, 250, 500, 1000, and 2000 micrograms/ml (ppm). Plasma AA concentrations were significantly elevated in chicks receiving 250 ppm AA or greater. In Trial 2, plasma AA concentrations increased significantly within 4 hr of supplementation in chicks receiving 1000 ppm AA. Statistically, maximum AA values occurred some 8 hr following the initiation of supplementation. Removal of the supplemented water resulted in rapid declines in plasma AA in Trial 3. Plasma AA values significantly higher than controls were maintained 16 hr after the removal of the supplemental water. Values returned to those of controls within 20 hr.