Iron absorption and rates of iron accumulation were analysed in a group of patients with β-thalassæmia intermedia. Iron absorption was strikingly increased and there was a progressive iron loading with increasing age. Balance studies indicated that by the time many of these patients reach the third or fourth decades their total iron loads may be of a similar magnitude to those of transfusion-dependent β-thalassæmia homozygotes. If these patients are to be protected from cardiac, hepatic, and endocrine complications of iron overload in middle life it will be necessary to reduce gastrointestinal iron absorption, starting from early childhood.