Patients have a blood test once a week while receiving rituximab to evaluate blood counts. After treatment is completed, patients are evaluated once a month until 6 months, then once a year until 3 years to monitor the response to treatment and any drug side effects. Patients are evaluated at NIH for the 3- and 6-month visits and the annual visits. They may be seen at NIH or by their referring doctors for the 1-, 2-, 4- and 5-month visits. A blood test is done at every visit, and a bone marrow aspiration and biopsy are done at the 3-month visit (and when clinically needed to evaluate the effect of rituximab on bone marrow cells).