Abstract: Respiratory function tests and arterial blood gas analysis were performed on 59 patients with β-thalassemia major (27 M, 22 F, age range: 18-45 years). All investigations were performed 24 h before the patients received a blood transfusion or when they were in a stable state hematologic condition. Echocardiography was performed in all patients and the ejection fraction was employed as a measure of cardiac function. No patient had clinical signs of pulmonary dysfunction. Pulmonary function tests, however, showed a reduction of all main parameters (TLC, FEV1, FEV1/FVC, FEF 25-75% and RV) in most patients with β-thalassemia major, indicating a restrictive type of dysfunction. Arterial blood gas values were within the normal range. There was no evidence that the observed abnormalities in pulmonary function were secondary to congestive heart failure. The low hemoglobin concentration and a fall in the diffusing capacity of the alveolar-capillary membrane, together with the dependence of the reduced pulmonary diffusing capacity on age and serum ferritin levels, as well as of the entity of restrictive disease on age, suggests that pulmonary dysfunctions in patients with TM are due mainly to lung fibrosis and/or interstitial edema related to iron overload. Also iron deposition due to repeated blood transfusions may play a central role in determining lung alterations although the majority of patients are well chelated, suggesting that more than one causal mechanism could be involved.