Studies were conducted to determine the iron requirements of laying and breeding hens (Gallus domesticus). Single Comb White Leghorn hens fed a purified diet containing 15 ppm iron exhibited a rapid decline in hematocrit, blood hemoglobin, egg iron concentrations and hatchability of fertile eggs. No effects of the low iron diet on body weight, feed consumption, or fertility were observed. When hens were fed graded levels of iron from 15 to 65 ppm at 10 ppm increments, a dose response was observed for hematocrit and hatchability. The iron requirement for maintenance of hematocrit was between 35 and 45 ppm iron. Fifty-five parts per million iron were required for maximum hatchability of fertile eggs.