The effects or oral supplementation of manganese, cobalt and molybdenum on growth rate and ascorbic acid metabolism was studied using guinea pigs maintained both on scorbutogenic and ascorbic acid supplemented diets. All the 3 metal ions lead to a decrease in weights of the animals of both the groups as compared to their respective controls; the decrease being more with Mn 2+ and Mo 6+ than with Co 2+ Dehydroascorbatase activity increases considerably in the scorbutic group and the administration of any one of the 3 metal ions to the animals of this group brings down this increase considerably, whereas the activity of uronolactonase which also increases under scorbutic conditions is not affected by the metal ions. In the ascorbic acid supplemented groups of animals, the metal ions are devoid of any significant effect on the dehydroascorbatase activity, whereas they stimulate the uronolactonase activity. L xylulose synthesis is inhibited under scorbutic condition. Mn 2+ inhibits L xylulose in both the groups, but Mo 6+ and Co 2+ are devoid of any effect. Ascorbic acid contents of liver, spleen, kidney and adrenal, which are decreased to a great extent under scorbutic conditions, are further decreased by the metal ions in all the tissues except spleen and adrenal by Mo 6+. In the ascorbic acid supplemented groups, ascorbic acid contents of all the tissues studied except kidney are decreased by the metal ions.