Essential thrombocythemia (ET), polycythemia vera (PV) and primary myelofibrosis (PMF) belong to the group of Philadelphia chromosome-negative myeloproliferative neoplasia (Ph- MPN). MPNs are clonal bone marrow stem cell disorders characterised by a proliferation of one or more of the myeloid, erythroid or megakaryocytic cell lines. Due to the different affected cell lines, MPNs show typical clinical and histological features. In 2005, a mutation in the JAK2 gene was discovered which generated more insight into the pathogenetic working mechanism of MPNs. However, the treatment of MPN patients is still mainly only palliative, although progress in reducing the symptoms of MPN patients has been made. This review will give a general overview of MPN patients for internal medicine physicians.