Treatment of anemia with human recombinant erythropoietin (EPO-R) and its effect on bone marrow was studied in 10 anemic patients on periodic hemodialysis (HD). Blood transfusion was not required once treatment started. Hemoglobin (Hb) levels normalized at six months in all patients (7.2 +/- 0.2 vs 12.4 +/- 3 g/dl, p less than 0.01). Serum ferritin levels decreased progressively as Hb increased (r = -0.5609), and six patients needed iron supplement since the third month. Bone marrow iron deposits decreased significantly (p less than 0.001), together with an increase of cellularity and improvement of erythrodysplasia. EPO-R was associated with worsening hypertension in previously hypertensive patients, although it could be controlled with more aggressive treatment. Thrombotic events either systemic or at the vascular access, were not observed. EPO-R corrects the anemia in uremic patients undergoing HD. Iron stores and blood pressure in hypertensive patients on treatment with EPO-R must be monitored regularly.