1. The concentrations of reduced ascorbic acid present in the tissues of normal rhesus monkeys are of a magnitude in keeping with the values found for other animal species which are incapable of synthesizing vitamin C. These concentrations are subject to distinct increase by prolonged parenteral administration of ascorbic acid. 2. The amounts of vitamin C present in nervous tissue and the suprarenals of monkeys, paralyzed as the result of poliomyelitis infection, are slightly below the normal average when examined at the height of paralysis or in early convalescence. The figures show a tendency for a return to normal or slightly hypernormal levels concomitant with the progress of convalescence. 3. Vitamin C titrations of the tissues of monkeys which had received parenteral injections of ascorbic acid during the incubation period of poliomyelitic infection give different results according to whether such animals develop paralysis or survive without paralytic symptoms. In paralyzed C-treated monkeys the vitamin C levels are practically identical with those of normal C-prepared monkeys. Markedly higher values, however, are obtained with non-paralytic survivors in the early stages of their survival. As the period of survival lengthens normal figures prevail again. 4. The data are discussed in their relationship to the success or failure of vitamin C therapy in experimental poliomyelitis.