Chronic myelomonocytic leukaemia (CMML) is a clonal disorder of the haematopoietic stem cell characterised by the presence of an absolute monocytosis in peripheral blood. The disease carries myelodysplastic and myeloproliferative features. This dilemma was sought to be overcome by the World Health Organization (WHO) in 2001, when CMML was classified within a new category of myelodysplastic syndromes/myeloproliferative neoplasms (MDS/MPN). The identification of molecular markers in patients with CMML has dramatically increased over the past couple of years. However, the impact on prognosis and therapeutic interventions needs to be defined. Testing of new agents in the setting of CMML proves to be difficult due to limited number of patients. This review has a focus on current diagnosis including new molecular data and treatment of CMML.