This single arm study will evaluate the safety and efficacy of MabThera maintenance therapy following a MabThera-containing induction regimen in first line or relapsed patients with follicular non-Hodgkin's lymphoma. All patients will receive MabThera 375mg/m2 body surface area, as an intravenous infusion, every 8 weeks. The anticipated time on study treatment is 1-2 years, and the target sample size is 500+ individuals.