Abstract Pantothenic acid was determined in five-day composites of food and twentyfour hour collections of the milk and urine of seven multiparas during two five-day periods immediately post partum and of nine nursing mothers during seventeen five-day periods at intervals during the production of mature milk. The average daily intakes of pantothenic acid ranged from 6.0 to 9.5 milligrams. During the first ten days post partum, daily secretion in milk rose with increasing volumes of milk produced. During the five days immediately following delivery, the intakes of six women were 0.46 to 2.78 mg. in excess of secretion in the milk and excretion in urine; during the next five days the milk and urine of four of the women contained averages of more pantothenic acid than their diets furnished. During the periods of mature milk production, 49 to 103 per cent of intake was found in milk and urine. The urine alone contained 32 to 89 per cent of the average daily intakes during the five-day periods.