Inclusion Criteria:

• Patients with CD 20 positive, relapsed/refractory indolent lymphoma. (Regimens of prior chemotherapy are limited to 2. Prior rituximab treatments up to 16 times are allowed.)
• Patients with measurable lesions (> 1.5 cm).
• Patients who have not received any treatment for more than 4 weeks after completing previous therapies (6 months in the case of antibody therapies).
• ECOG performance status: 0 - 1
• Patients with adequately maintained organ functions.

Exclusion Criteria:

• Patients with infectious disease, serious complications, serious gastrointestinal symptoms, serious bleeding tendency, serious CNS symptoms, fever </=38 °C, interstitial pneumonia or pulmonary fibrosis, active other malignancies, autoimmune hemolytic anemia or the history of the disease, or glaucoma.
• Patients who are positive for HBs antigen, HCV antibody, or HIV antibody.
• Patients who received G-CSF or transfusion within 1 week before the registration.
• Patients with the history of allergies to purine nucleoside analogue.
• Patients who experienced serious hypersensitivity or anaphylaxis to rituximab or mouse protein-derived products.
• Patients who had ever received prior therapy with fludarabine phosphate injection, pentostatin, cladribine, SH T 586, blood stem cell transplant, or monoclonal antibody therapy other than rituximab to NHL (including radioimmunotherapy).
• Patients who had progressive disease within 6 months of receiving therapy including rituximab.
• Women who are pregnant, of childbearing potential, or lactating.
• Patients who do not agree to practice contraception.