Year old dogs were placed on a vitamin A-deficient diet, litter-mate controls, however, were placed on the same diet plus cod liver oil. A neutrophil index lag (modified Arneth index) was the earliest manifestation of the cellular changes associated with vitamin A-deficiency in the dog. Xerophthalmia and loss of weight were not observed within one year. Early metaplasia of the bronchiolar epithelium, with pneumonitis, furnished further evidence of the A-deficiency. Spectrophotometric assay of the livers showed essential depletion. Of the vitamin A units given in the form of cod liver oil, 44% were recovered from the liver. Following the administration of a massive dose of vitamin A to A-deficient dogs, a three months'' old puppy absorbed and assimilated in the liver about 40 times as much vitamin A as did an adult dog. From the evidence presented the vitamin A utilization rate in the dog is between 157 and 330 I.U./kg./week. The comparable daily requirement of vitamin A for a man weighing 60 kgm. would be 1800 I.U. or approximately 2 g. of cod liver oil.