2. i) Diagnosis of aggressive CD20+ B-NHL with measurable tumor burden (by imaging, flow cytometry and/or PCR) post-treatment. This includes patients with persistent disease following more than 2 lines of chemotherapy, as well as patients who relapse following autologous transplantation, and in whom further salvage therapy has produced only a partial remission or where no effective salvage therapy available. Patients with bulky disease who require immediate salvage therapy will not be eligible.