Children with Down syndrome (DS) are at increased risk of leukaemia. Myeloid disorders include transient abnormal myelopoiesis (TAM), myelodysplasia (MDS) and acute myeloid leukaemia (AML). Mutations in the GATA-1 gene, which encodes for a transcription factor central to the normal development of the erythroid and megakaryocytic lineages, are found in cases of TAM, MDS and AML in DS children. DS children with MDS/AML mostly present between the ages of 1 and 4 years, and have a large predominance of megakaryoblastic disease (French-American-British type M7). The MDS and AML are part of a single disease entity (myeloid leukaemia of Down syndrome) that is extremely sensitive to chemotherapy. Resistant disease and relapse are rare, but treatment-related toxicity is high, and deaths in remission have exceeded those due to disease in most series. Accordingly, controlled dosage reduction is the focus of contemporary treatment studies.