Antibodies to HTLV-III were found in 6 of 206 Sicilian patients with thalassemia major, aged 1 to 30 years. None of the patients showed clinical signs related to immuno-deficiency syndromes. Immunological investigations carried out in all positive patients showed alterations similar to those found in thalassemic patients without antibodies to HTLV-III. These immunological changes could not depend on the HTLV-III infection, but could be related to the thalassemic condition.