Serum ferritin concentration was assessed in male and female pregnant and non-pregnant thalassaemia carriers and in normal subjects of both sexes. Low ferritin levels were found in 61% of non-pregnant and in 32% of pregnant female β-thalassaemia heterozygotes whereas male thalassaemia carriers had normal iron stores. Increased ferritin levels were not observed in any of the subjects examined. These findings show that iron deficiency is a common finding in female thalassaemia carriers of reproductive age who are not receiving iron supplementation.