Objective: Our aim for this study was to describe the outcome of blood and marrow transplantation in patients with class 3 thalassemia major. Method and patients: Since December 1992 till October 2002, forty-three patients with thalassemia class 3 received blood and marrow transplantation from their HLA-identical siblings. Median age at time of transplantation was 8 years (age range = 3–17), Male/Female = 24/19. Twenty-eight patients received bone marrow and fifteen patients received peripheral blood stem cell transplantation. Conditioning regimen was cyclophosphamide 40 mg/kg/day (from day–5 to -1) and busulfan 4 mg/kg/day (from day –9 to -6). GVHD prophylaxis regimen was cyclosporine A 3mg/kg /day/iv (from day −2 to +5) then 12.5 mg/kg/day/po (from day +5) and methotrexate 10mg/m2 (day +1), 6mg/m2 (days +3, +6). Results: Median time of absolute neutrophil count ≥ 0.5 × 109 /L was on day +20 and Median time of platelet recovery ≥20 × 109 /L was on day +25. At present 34 out of 43 are alive and 9 patients died due to aGVHD, cGVHD, rejection, veno-occlusive disease, infection and the others. Thirty-two patients (74.4%) developed aGVHD (grade I = 9, grade II = 7, grade III = 11, grade IV = 5). Seventeen patients (39.5%) developed cGVHD (limited = 5, extensive = 12). Eight year disease free survival in class 3 and 2 were 71% and 63%, respectively (p = 0.3).Eight year overall survival in class 3 and 2 were 78% and 79%, respectively (p = 0.00). Conclusion: According to this study, for an acceptable outcome in thalassemia class3. We need better conditioning and GVHD prophylaxis regimens to decrease cardiopulmonary and liver complications. The results of blood and marrow transplantation showed that it is better than supportive therapy such as transfusion and desferal therapy. Objective: Our aim for this study was to describe the outcome of blood and marrow transplantation in patients with class 3 thalassemia major. Method and patients: Since December 1992 till October 2002, forty-three patients with thalassemia class 3 received blood and marrow transplantation from their HLA-identical siblings. Median age at time of transplantation was 8 years (age range = 3–17), Male/Female = 24/19. Twenty-eight patients received bone marrow and fifteen patients received peripheral blood stem cell transplantation. Conditioning regimen was cyclophosphamide 40 mg/kg/day (from day–5 to -1) and busulfan 4 mg/kg/day (from day –9 to -6). GVHD prophylaxis regimen was cyclosporine A 3mg/kg /day/iv (from day −2 to +5) then 12.5 mg/kg/day/po (from day +5) and methotrexate 10mg/m2 (day +1), 6mg/m2 (days +3, +6). Results: Median time of absolute neutrophil count ≥ 0.5 × 109 /L was on day +20 and Median time of platelet recovery ≥20 × 109 /L was on day +25. At present 34 out of 43 are alive and 9 patients died due to aGVHD, cGVHD, rejection, veno-occlusive disease, infection and the others. Thirty-two patients (74.4%) developed aGVHD (grade I = 9, grade II = 7, grade III = 11, grade IV = 5). Seventeen patients (39.5%) developed cGVHD (limited = 5, extensive = 12). Eight year disease free survival in class 3 and 2 were 71% and 63%, respectively (p = 0.3).Eight year overall survival in class 3 and 2 were 78% and 79%, respectively (p = 0.00). Conclusion: According to this study, for an acceptable outcome in thalassemia class3. We need better conditioning and GVHD prophylaxis regimens to decrease cardiopulmonary and liver complications. The results of blood and marrow transplantation showed that it is better than supportive therapy such as transfusion and desferal therapy.