Superoxide anion production in resting and PMA- or zymosan-stimulated neutrophils was evaluated in 21 β-thalassemia patients. The results were correlated with ferritin values, hepatitis B virus serum markers, liver pathology, immunoglobulin levels and T-cell subsets. Superoxide anion generation from resting or PMA-stimulated neutrophils was significantly higher in patients than in controls. On the contrary, zymosan-stimulated neutrophils showed reduced superoxide anion production. Increased superoxide anion production in resting neutrophils showed a significant correlation to the values of ferritin. In addition, patients with biopsy-proven chronic liver disease showed significantly increased ferritin levels and superoxide anion production as compared to the remaining patients. No correlation was observed between superoxide anion production and the presence or the absence of hepatitis B virus serum markers, immunoglobulin levels and T-cell subsets. A possible role of interreactions between iron and oxygen radicals in determining liver damage in β-thalassemia patients is suggested.