 In Latin America, there are no epidemiological studies with a great number of Ph-negative MPN patients describing the natural history of the disease, patient progress, clinical characteristics, standards of care and disease burden. The development of an up-to-date data registry of Brazilian patients with Ph-negative MPN allows the comprehension of the epidemiology of this disease, with determination of survival, thrombosis incidence, transformation to AML, use of disease treatment-related resources, as well as the impact of different therapeutic strategies in these parameters. Therefore, the objective of this study is to establish a registry of patients with Ph-negative MPN in order to document the disease diagnosis and current standards of care, clinical endpoints, and the use of treatment-related resources, according to risk classification in each MPN. 