1. Copper deficiency was induced in growing rabbits and the effects of ascorbic acid supplementation were studied.
2. Signs of Cu deficiency, including reduced growth, achromotrichia and alopecia, anaemia, and gross alterations in the bones of the forelimbs, developed most rapidly in those animals fed ascorbic acid.
3. Microscopic lesions in ossification centres were seen only in bones of rabbits which hadm received the vitamin.
4. Calcium and phosphorus contents of ash from cortical bone were not changed.
5. Compared with the controls, the concentration of liver Cu decreased and that of iron increased (> 50%) in Cu-deficient animals.
6. Cytochrome oxidase activity was reduced in liver and heart in Cu-deficient animals; this effect was accentuated in heart preparations from animals fed ascorbic acid.