Here we describe the case of a 30-year-old man with a diagnosis of de novo acute monoblastic leukemia (FAB M5a), whose karyotype analysis revealed the presence of the translocation (8;21)(q22;q22) as the sole chromosome anomaly. In spite of the rather good prognosis patients suffering from acute leukemia and carrying this translocation are supposed to have, our patient had a very poor outcome, including an early relapse resistant to any treatment and meningeal localization. Death occurred within 5 months from diagnosis. To our knowledge this is the first report of t(8;21)(q22;q22) in de novo acute monoblastic leukemia.