The FAB group has recently published guidelines for distinguishing chronic granulocytic leukaemia (CGL) from chronic myelomonocytic leukaemia (CMML) and atypical chronic myeloid leukaemia (aCML). Whereas CGL is generally recognized to be a distinct entity, there is debate as to whether CMML and aCML are separate disorders or part of a spectrum of myeloproliferative disorders with dysplastic features. Data are presented on 10 cases who developed features of a CML during the course of their disease but who presented with a normal or a low leucocyte count without a monocytosis and were diagnosed as refractory anaemia. This suggests that, at least in some cases, aCML represents an unusual evolution of MDS, and even though these patients have a uniformly poor prognosis it may be premature to regard aCML as a distinct clinical entity.