Turkey poults, when fed a highly purified diet containing all necessary nutrients except nicotinic acid, grew poorly and developed certain deficiency symptoms such as inflammation of the mouth, diarrhea, low feed consumption, poor efficiency of feed utilization, poor feathering, and perosis. The perosis in the deficient birds occurred in spite of ample manganese, choline, and biotin in the diet. All symptoms were prevented by the addition of 3 to 5 mg. of nicotinic acid per 100 gm. of ration. Higher levels of nicotinic acid, however, may be needed for optimum growth.