Traditionally the excess platelet and white cell production in ET, PV and PMF has been treated with cytoreductive agents such as hydroxyurea and busulfan in order to normalize the blood counts and thereby reducing the risk of thrombosis. However, in younger patients there is a concern of the leukemogenic potential of these agents. In younger patients an alternative treatment option is recombinant pegylated interferon alpha (IFN-alpha), which has demonstrated high clinical efficacy and has no leukemogenic potential. Within recent years IFN-alpha has demonstrated a capacity of inducing deep molecular remission (evaluated by JAK2 V617F qPCR) and normalisation of bone marrow morphology. These remissions have been sustained for up to 3 years after discontinuation of IFN-alpha therapy. Accordingly a perspective of changing the natural history of these disorders towards myelofibrosis and ultimately acute leukemia has emerged. However toxicity has been a major issue and drop-of rates have been reported consistently around 25 %.