Myelodysplastic syndromes (MDS) in children constitute a heterogeneous disorder, including 'primary' MDS and MDS associated with constitutional abnormalities. The Franco-American-British (FAB) cytological classification for adults can be applied for childhood in 50 to 100% of the cases. The transformation into acute myeloblastic leukemia often occurs, but stabilisation or spontaneous regression of the disease may also be observed. The therapeutic decision is difficult because there is no predictive factor of the course of the disease. Allogenic bone marrow transplantation is the best curative option when treatment is necessary.