Patients return to the National Institutes of Health (NIH) Clinical Center for frequent follow-up visits during the first 2 to 3 months following transplant. The time between visits is then extended to once every 3 months the first year, then every 6 months the second year, and then at least yearly for 5 years after the transplant. These visits include a physical examination, blood and urine tests, lumbar puncture (if there is central nervous system involvement), other appropriate biopsies and tests as needed to monitor the patient's health, short apheresis procedures to collect blood for research purposes, and quality of life questionnaires. Some select procedures will be optional. Bone marrow biopsies and lymph node aspirates are done at beginning and at 6, 12, and 24 months after transplant. PET scans are done at 1, 6, 12, and 24 months.