Sickle cell disease is a hemoglobin disorder which is characterized by live-threatening organ damage, both acute and chronic. It can be cured by bone marrow transplantation (BMT), mortality and severe morbidity being 10-15%. Severity of clinical manifestations in sickle cell disease varies considerably from patient to patient. As there are as yet no reliable criteria to predict a patient's individual course there is a dilemma when it comes to selecting patients for BMT. The presently existing protocols for BMT in sickle cell patients, Belgian, American and a British, are selecting patients who already had severe clinical problems without, however, showing signs of irreversible organ damage. As the number of sickle cell patients in Germany is very small (ca. 250) we plan to join one of the existing BMT studies.