12 patients with myelodysplastic syndromes were treated with recombinant human erythropoietin (r-epo). 5 patients had stable anemia, 78-92 g/l, and 7 were transfusion-dependent. In 11 patients, r-epo was given intravenously three times a week, with dose escalation after 4 and 8 wk if hemoglobin did not increase more than 15 g/l. The doses were 600, 1500 and 3000 U/kg bodyweight/wk. The 12th patient was treated subcutaneously with a dose of 560 U/kg/wk. 3 patients showed a significant response with an increase in hemoglobin of greater than or equal to 15 g/l. 2 of these had stable anemia before treatment and increased in hemoglobin from 87 to 116 g/l and from 80 to 99 g/l, respectively. The 3rd patient was transfusion-dependent and rose to a stable hemoglobin level between 76 and 80 g/l without transfusions. 2 patients showed a reduction of their transfusion need. Mean initial serum erythropoietin in the responding group was 366 U/l compared to 1049 among the non-responders (p = 0.367). Response was observed in 5/7 patients without bone marrow sideroblasts and in 0/5 patients with sideroblasts (p = 0.027). Erythropoietin seems to be an effective and well-tolerated treatment for a certain proportion of patients with MDS. A larger patient material might provide a model for predicting responses.