Individuals with a certain type of beta thalassemia that is treated with regular transfusions, and who are 50 years old and younger, may be able to participate. A number of screening tests will be done to determine if subjects can participate. These include review of your past medical history, blood and urine tests, bone marrow aspirate/biopsy, bone age/ DEXA scan, heart ultrasound, electrocardiogram, magnetic resonance imaging (MRI) of the heart and liver, and liver biopsy. If eligible, blood stem cells will be collected by apheresis or by bone marrow harvest. These stem cells will then have a healthy beta globin gene inserted. You will then be hospitalized and chemotherapy will be given to empty out the bone marrow. The stem cells, with the inserted gene, will then be given back to you. You will be followed for side effects and to see if the inserted gene helps you make hemoglobin.