Serum lipids, phospholipid fractions and the composition of serum lipid fatty acids were studied in 20 children presenting β-thalassaemia major, 20 heterozygous children and 20 normal controls. Total serum phospholipids, their fractions and cholesterol were significantly lower in patients with thalassaemia major. These changes were referred to hepatic damage and to severe anaemia, respectively. Some serum lipid polyunsaturated fatty acids were significantly decreased in patients with thalassaemia major as compared to heterozygotes and normal controls. Since these alterations are a sign of lipid oxidation, the causes of this phenomenon are discussed.