conclusions1Young rabbits fed a purified ration supplemented with pure vitamin preparations grew at a nearly normal rate.2Rabbits fed this purified diet require niacin for survival and adequate growth.3Symptoms shown by rabbits receiving the niacin deficient diet are loss of weight and usually severe diarrhea 24 to 48 hours before death.4Rabbits fed the diet containing adequate amount of niacin but pair-fed with litter mates receiving the niacin deficient ration died as early as the deficient animals and showed simliar symptoms.5Rabbits fed the niacin deficient diet for 3 months or longer showed significantly less niacin in the voluntary muscles than the litter mates given niacin.