In a cytogenetic study of 54 patients with acute monoblastic leukaemias (AML5) two had a (9;11) (p21;q23) translocation. In addition to the clone, with t(9;11), both patients had a second clone with t(9;11) and trisomy 8. These two patients were aged 23 and 35 years at diagnosis and were classified as M5a in the FAB formulation. A complete remission was achieved in each case, persisting after 19 and 18 months respectively (autograft for one patient). Whereas chromosome 11 anomalies are involved in 13% of all AML5 cases, t(9;11) is less frequently encountered (3.7% in our experience).