Iron deficiency, defined as a serum ferritin level less than or equal to 50 micrograms/l was found in 28 (11%) of 252 consecutive elderly in-patients (mean age 81 years). Sixteen among them were anaemic and only five had a microcytic anaemia. In a separate study, 15 anaemic and 13 non-anaemic iron-deficient elderly in-patients were investigated in order to evaluate the prevalence of gastrointestinal symptoms and lesions in both groups. In nine of the anaemic and seven of the non-anaemic patients a potential cause for the iron deficiency was established. Most anaemic and non-anaemic patients lacked the symptoms described as suggestive of underlying gastrointestinal pathology. Thus, a ferritin level less than or equal to 50 micrograms/l justifies a gastrointestinal investigation if the general condition allows for it as well in anaemic as in non-anaemic elderly hospitalized patients. Therefore, serum ferritin should be part of the routine biochemical investigation of elderly in-patients.