In thalassemia after successful bone marrow transplantation (BMT), iron overload remains an important cause of morbidity. After BMT, patients have normal erythropoiesis capable of producing a hyperplastic response to phlebotomy so that this procedure can be contemplated as a method of mobilizing iron from overloaded tissues. A phlebotomy program (6 mL/kg blood withdrawal at 14-day intervals) was proposed to 48 patients with prolonged follow-up (range, 2 to 7 years) after BMT. Seven patients were not submitted to the program (five because of refusal and two because of reversible side effects). The remaining 41 patients (mean age, 16 +/- 2.9 years) were treated for a mean period of 35 +/- 18 months. All were evaluated before and after 3 +/- 0.6 years of follow-up. Values are expressed as mean +/- standard deviation (SD) or as median with a range (25 to 75 percentile). Serum ferritin decreased from 2,587 (2,129 to 4,817) to 417 (210 to 982) microg/L (P < .0001), total transferrin increased from 2.34 +/- 0.37 to 2.7 +/- 0.58 g/L (P = .0001), transferrin saturation decreased from 90% +/- 14% to 50% +/- 29% (P < .0001). Liver iron concentration evaluated on liver biopsy specimens decreased from 20.8 (15.5 to 28.1) to 4.2 (1.6 to 14.6) mg/g dry weight (P < .0001). Aspartate transaminase decreased from 2.7 +/- 2 to 1.1 +/- 0.6 (P < .0001) and alanine transaminase from 5.2 +/- 3.4 to 1.7 +/- 1.2 (P < .0001) times the upper level of normality. The Knodell score for liver histological activity decreased from 6.9 +/- 3 to 4.9 +/- 2.8 (P < .0001). These data indicate that phlebotomy is safe, efficient, and widely applicable to ex-thalassemics after BMT.