Labeled hydroxocobalamin, administered intramuscularly in man, is absorbed more slowly from the site of injection and deposited in the liver and calf muscle to a degree equal to or higher than that of cyanocobalamin at an equivalent dose. These findings, together with those reported in Part I of this paper, suggest the applicability of hydroxocobalamin as a long-acting vitamin B12 in man. These conclusions, however, require the support to be obtained from long-range observations on patients with vitamin B12 depletion.