Stored iron readily available for hemoglobin synthesis was measured by means of repeated phlebotomy in 13 carefully selected normal young men and women. The stores of the males averaged 819 mg, while those of the 10 normal nulliparous women averaged only 254 mg or about one-third as much as in the males. The ability of orally administered iron to regenerate iron stores was studied in six of these previously normal volunteers, and in three women who had become iron depleted and severely anemic due to menorrhagia. It was demonstrated that iron stores can be replenished with iron administered orally, but to accomplish this the medication must be continued for several months after the hemoglobin concentration has returned to normal.