Five cases of acute myeloblastic leukaemia (AML) arising in the course of non-Hodgkin's lymphoma (NHL) are described. The initial lymphoma was nodular lymphoid poorly differentiated in 4 cases. All patients were under chemotherapy for at least 28 months, and 3 of them were irradiated. AML was diagnosed 44 to 78 months after NHL and was heralded in 3 cases by a preleukaemia phase of pancytopenia. The leukaemia was typically myeloblastic in 2 cases and difficult to classify in 3 cases. Death occurred rapidly in 4 patients. The actuarial risk was 4.5% at 5 years. Since AML's occur mainly in NHL's, the management of this type of lymphoma with favourable prognosis ought to be reevaluated.