The anti-CD20 monoclonal antibody rituximab, first approved for clinical use in 1997, has changed the standard of care for many patients with non-Hodgkin's lymphoma (NHL). Recent data from large randomized clinical trials confirm that the addition of rituximab to standard chemotherapy regimens (chemoimmunotherapy) improves both response rates and survival outcomes in patients with follicular NHL and diffuse large B cell lymphoma (DLBCL), the two most common subtypes of NHL. Population-based analyses have found substantial improvements in NHL survival over the past decade; studies indicate that rituximab has favorably altered the long-term prognosis of follicular NHL and DLBCL patients. This review discusses the clinical development of rituximab-based therapies for patients with low-grade or follicular NHL and newly diagnosed DLBCL, highlighting recent key randomized trials with a focus on survival outcomes.