These studies examined the bioavailability of iron in iron-enriched breads. The test breads also contained added protein in the form of gluten, soy or nonfat dry milk. Bioavailability was assessed based on net hemoglobin synthesis in rats initially made iron deficient and then fed bread-based diets containing 38.5 ppm iron (NRC requirement for rat, 35 ppm) and 3.75, 5.00, or 6.25 ppm copper (NRC requirement for rat, 5 ppm). More hemoglobin was synthesized on milk-supplemented (83 mg/mg iron) and on soy-supplemented (85 mg/mg iron) bread diets than on gluten-supplemented (59 mg/mg iron) bread diets. Copper appeared to have no influence on hemoglobin regeneration or on hepatic iron accumulation under the conditions of this experiment.