The influence of ascorbic acid supplementation on the copper status of young adult men was investigated. Subjects consuming self-selected diets took 500 mg of ascorbic acid with each meal (1500 mg/day) for 64 days. Blood samples were obtained at 0, 28, 52, and 64 days in order to determine serum copper and serum ceruloplasmin. Each subject thus served as his own control. Analyses were repeated 20 days after the ascorbic acid supplement was terminated. Serum ceruloplasmin activity was significantly reduced (p less than 0.01) at every data point throughout the ascorbic acid supplementation period. A similar but nonsignificant trend was observed for serum copper. Furthermore there was a significant increase (p less than 0.01) in serum copper concentration 20 days after the supplementation period. Although observed effects occurred within physiological ranges of normal values, this study confirms that a high ascorbic acid intake is antagonistic to copper status of men as has been demonstrated in laboratory animals.