Absorption from a 5 mg dose of iron as Fe++ or haemoglobin iron was studied using a Total Body Counter in control subjects and patients with coeliac disease. In both groups the majority of subjects were iron deficient. Thirteen control subjects, 13 patients with untreated coeliac disease and 14 on treatment with gluten-free diet had both absorption tests. Absorption of Fe++ iron was reduced in untreated coeliac disease. This was particularly significant in iron deficient patients. Absorption was improved on treatment with gluten-free diet; In contrast, the absorption of haemoglobin iron was not affected in coeliac disease, indicating that absorption of iron in this form is not dependent on the integrity of the mucosa of the proximal small bowel.