We evaluated in a prospective pilot- study the effect of reduced intensity conditioning with busulfan (10 mg/kg), fludarabine (150 mg/m²) and anti-thymocyte globulin followed by allogeneic stem cell transplantation from related and unrelated donors in 14 patients with myelofibrosis. Study objectives were engraftment, chimerism, treatment- related mortality (TRM) and response. The median age of the patients was 51 (range, 32 – 63) years. According the Lille score there were low risk (n=4), intermediare risk (n= 7) and high risk (n=3) The median time until leukocyte (> 1.0 x 109/l) and platelet (> 20 x 109/l) engraftment was 16 (range, 11 – 26) days and 26 (range, 9 – 139) days, respectively. No graft failure occurred. Complete donor chimerism on day 100 was seen in 13 patients (93%). Acute graft-versus host disease (GvHD) grade II-IV occurred in 50% and grade III/IV 29 % of the patients. The incidence of chronic GvHD was 54 %. Two patients died due to treatment complications, resulting in a TRM at one year of 15% (95% CI: 0–35%). Hematological response after allogeneic transplantation was seen in all patients and complete histopathological remission was observed in 90%of patients. After a median follow-up of 13 (range, 3 – 48) months, the 3-years estimated overall and disease-free survival is 85 % (95 % CI: 65–100 %).