Although the French-American-British (FAB) morphologic classification of myeloid malignancies has been accepted for many years, the important advances in cytogenetic, immunophenotype and genetic fields needed to be integrated in an updated approach using all the available informations. Thus, the World Health Organization (WHO) Classification of haematopoietic malignancies not only incorporates morphology, immunophenotype, cytogenetic and molecular features, but also ensures to be clinically useful. This collaborative project has begun in 1995 and has been published in 2001. The proposed WHO classification is less a disruption with regard to the FAB classification than an updated revision where morphology is always important. These review emphasises the modifications proposed in the new WHO classification concerning the myeloid disorders.