A total of fifty severely affected patients with homozygous sickle cell disease or other sickling disorders (e.g., B negative or B positive Thalassemia/Sickle) who are greater than 18 years of age will be eligible for treatment. Such patients must be able to tolerate an extensive period without blood transfusion and have relatively well preserved renal and hepatic function (creatinine less than 1.5 mg/dl and normal liver function test with exception of a mild elevation in transaminase). Evidence of severe sickle cell anemia will include recurrent pain crisis, chronic bone pain, evidence of aseptic necrosis with symptoms, and intractable leg ulcers, etc.