The myeloproliferative neoplasms, are characterised by overproduction of myeloid cells. Chronic myeloid leukaemia, polycythaemia vera, essential thrombocythaemia, myelofibrosis and the very rare disorders chronic neutrophilic leukaemia, chronic eosinophilic leukaemia not otherwise specified and mastocytosis are all included in the group. Incidence and prevalence rates reported in the worldwide literature are presented in this review. Survival data on each condition is described. Information on the aetiology of the disorders is discussed including body mass index, diet, smoking and alcohol, allergies, associated medical conditions, occupation and environmental exposures with focus on recent new studies. The aetiology of the myeloproliferative neoplasms remains unknown, and this review of the current state of knowledge highlights the need for further comprehensive research.