A previously reported study by Kemp and Calabrese1indicated that ascorbic acid reduces the occurrence of copper acetate‐induced methemoglobin (METHB) formationin vitro.The present study was designed to evaluate these findings in anin vivoexposure of ascorbic acid (1 gm/day) for up to four weeks with anin vitrocopper acetate incubation stress at baseline (just prior to supplementation) and at two and four weeks after initiation of treatment. The results indicated that the ascorbic acid supplementation had no significant effect on the occurrence of copper acetate induced oxidant stress (i.e. METHB increase and GSH decrease). Possible explanations for this apparent descrepancy are provided.