In order to decrease drop out rates and thereby increasing response rates patients will be started of at a low-dose of IFN-alpha. If patients fail to respond or looses their response and develops neutralizing antibodies against IFN-alpha therapy will be stopped. If patients have a sustained deep molecular response (below 1 % JAK2 V617F mutated alleles for 12 months) therapy will be stopped to asses the sustainability of the remission off therapy.Patients over the age of 75 and intolerant or resistant to hydroxyurea will be offered rescue treatment with orally busulfan (Myleran). As an important part of the study quality of life will be investigated.