This report describes a case of t(15;17) acute promyelcytic leukaemia (APL, FAB subtype M3) with dysgranulopoiesis at diagnosis in a patient who developed myelodysplasia (MDS) and then a second phenotype of t(7;21) acute myeloblastic leukaemia (AML, FAB subtype M1) at the time of relapse. To our knowledge, there is no report of a second phenotype of AML occurring after complete remission (CR) of APL. Furthermore, this is the first report of chromosomal abnormality t(7;21) in a case of AML. Several hypotheses for this unusual course of APL are discussed.