Pyridoxine deficiency in young monkeys resulted when a synthetic diet was fed with all the crystalline vitamin B complex except pyridoxine. The symptoms were lack of growth, ataxia, hypochromic microcytic anemia, mild leucopenia, polychromatophilia and the appearance of nucleated red blood cells. With the administration of pyridoxine, growth was resumed and the anemia and blood picture improved. A concomitant deficiency of the monkey anti-anemia factor occurred and was manifest by anemia and a reversal of the normal neutrophile/lymphocyte ratio. Whole liver substance at a level of 3% was necessary for optimum growth and blood regeneration. Pantothenic acid deficiency syndrome was characterized by lack of growth, ataxia, greying and thinning of the fur, anemia, diarrhea and cachexia. Incomplete remission of these symptoms occurred on the administration of calcium pantothenate but complete recovery resulted when whole liver substance at a level of 3% of the ration was given.