Abstract:We examined the efficacy and toxicity of recombinant interferon‐alpha2b (rIFN‐α2b) in 10 previously untreated patients with advanced myelodysplastic syndromes. Morphological subtypes were refractory anaemia with excess of blasts (RAEB) in 4, RAEB in transformation (RAEB/T) in 3 and chronic myelomonocytic leukaemia (CMML) in 3 cases. IFN was administered subcutaneously at increasing doses of 1 to 3 times 106IU per day. The median duration of therapy was 6 months (range, 3 to 14). 2 patients, both with a diagnosis of CMML, achieved a complete and partial remission, respectively. In the complete responder, remission could be maintained for 9.5 months by daily administration of 1 times 106IU IFN. The other patients were classified as failures, although in 4 cases a decrease of bone marrow blasts was noted and none of the patients progressed to overt leukaemia while being treated with IFN. During the study, all patients with RAEB and RAEB/T showed a moderate to severe reduction in peripheral leukocyte and platelet counts, requiring premature termination of IFN therapy in 5 cases. Despite adequate supportive measures, 2 patients died of pneumococcal pneumonia and gastrointestinal bleeding, respectively. In 1 patient, IFN therapy had to be stopped because of neurologic toxicity (polyneuropathy). From these data we conclude that rIFN‐α2b at the doses and schedule tried is not a useful treatment for advanced myelodysplastic syndromes. Patients with CMML, however, may be an exception and should further be considered as candidates for therapeutic trials with r