Iron tablets are widely used in the community. Severe, sometimes lethal, damage to the gastrointestinal tract following overdose is well known, but there is less appreciation of the damage that can be caused by therapeutic dosage. In this histological study of three esophageal lesions and six gastric lesions (including one autopsy case), heavy iron accumulation was demonstrated within ulcer granulation tissue, in connective tissue and blood vessels of the mucosal lamina propria, and within glandular and squamous epithelium. The appearance was distinctive and was similar to that seen following overdosage, although more localized. Five of the patients studied had evidence of delayed esophageal or gastric emptying which could have contributed to the damaging effect of the iron tablets. In most of the patients ulceration appeared to have preceded the commencement of iron therapy, so that the iron probably exacerbated rather than initiated ulceration and stricture formation. Histopathological reporting of iron-induced changes in endoscopic biopsies will alert clinicians to a correctable pathological process.