The serum levels, the biological activity and the phenotypes of α1-antitrypsin (α1AT) were determined in 158 /β-thalassaemic patients and in 504 healthy controls. The concentration and the activity of α1AT were found within normal limits. An increased frequency of the F gene, a decreased frequency of the M and a normal frequency of the Z gene were observed in thalassaemic patients. It can be suggested that the quantity and/or the activity of serum α1AT are not responsible for the respiratory infections encountered in many of the β-thalassaemic pat