Depletion of malignant B-cells using anti-CD20 monoclonal antibodies has an acceptable safety profile, particularly in patients with low-grade B-cell lymphomas with a low disease burden. To determine whether treatment with GA101 results in better outcomes than that seen with rituximab and to determine which anti-CD20 antibody to utilize in future studies, we will conduct a randomized Phase II trial of rituximab and GA101 in patients with previously untreated low-grade lymphoma. Patients will receive either rituximab or GA101 weekly for 4 weeks followed by re-staging. The endpoints of the study will be the Complete Response (CR), Overall Response Rate (ORR), time to next treatment, progression free survival (PFS), and safety of each treatment arm.