This randomized, noninferiority, global, phase 3 study evaluated the efficacy and safety of bendamustine plus rituximab (BR) versus a standard rituximab-chemotherapy regimen (rituximab plus cyclophosphamide, doxorubicin, vincristine, and prednisone [R-CHOP] or rituximab plus cyclophosphamide, vincristine, and prednisone [R-CVP]) for treatment-naive patients with indolent non-Hodgkin's lymphoma or mantle cell lymphoma. Investigators preassigned the standard treatment regimen they considered most appropriate for each patient; patients were randomized to receive BR (n = 224) or standard therapy (R-CHOP/R-CVP, n = 223) for 6 cycles; 2 additional cycles were permitted at investigator discretion. Response was assessed by a blinded independent review committee. BR was noninferior to R-CHOP/R-CVP, as assessed by the primary endpoint of complete response rate (31% vs 25%, respectively; P = .0225 for noninferiority [0.88 margin]). The overall response rates for BR and R-CHOP/R-CVP were 97% and 91%, respectively (P = .0102). Incidences of vomiting and drug-hypersensitivity reactions were significantly higher in patients treated with BR (P < .05), and incidences of peripheral neuropathy/paresthesia and alopecia were significantly higher in patients treated with standard-therapy regimens (P < .05). These data indicate BR is noninferior to standard therapy with regard to clinical response with an acceptable safety profile. This trial was registered at www.clinicaltrials.gov as #NCT00877006.