A patient with chronic myeloid leukemia (CML) treated with interferon alpha (IFN alpha) and who developed autoimmune hepatitis (AIH) is described. The patient was treated with IFN alpha 2a, a complete cytogenetic response was achieved 5 months later, and this response has lasted now more than 7 years. Autoimmune hypothyroidism appeared at 18 months of treatment, and 1 year later severe type I autoimmune hepatitis developed. To our knowledge this is the first report of such complication in an IFN alpha-treated CML patient.