This publication on the assessment of iron bioavailability was developed as part of the IAEA’s continuing efforts to transfer knowledge and technology on the use of stable isotope techniques in nutrition. It provides information on the theoretical background and practical application of state of the art methodology to measure human iron absorption and dietary iron bioavailability using stable (non-radioactive) isotopes. These techniques can be used to guide fortification and food based strategies to combat iron deficiency, which remains unacceptably high among infants, children and women of childbearing age in developing countries.