Background: This study was designed to investigate the activity and safety of rituximab (Rituxan®, R) plus CHOP induction therapy followed by maintenance R in patients with previously untreated advanced stage indolent NHL. The initial results of R-CHOP induction treatment are reported here.Methods: 102 patients with Ann Arbor Stage III or IV indolent NHL (follicle center/follicular grade I/II or nodal marginal zone B-cell by REAL; Type B or C by IWF) were enrolled into this open-label, multi-center, community-based, Phase II, single-arm trial. Patients received 6 cycles of standard R-CHOP induction therapy (cyclophosphamide 750 mg/m2, vincristine 1.4 mg/m2, doxorubicin 50 mg/m2 all IV on Day 1; prednisone 100 mg/day Days 1–5). R 375 mg/m2 was given on Day 1 of each cycle except for cycle 1, when it was administered 2–3 days prior to CHOP chemotherapy. Subjects with an ongoing response (CR/CRu or PR) after induction receive maintenance R (4 weekly infusions) within 28 days after the completion of induction and repeated every 6 months for 2 years for a total of 16 maintenance R doses. The primary endpoints were CR/CRu after 6 cycles of induction and the incidence of R infusion-related toxicity during induction and maintenance therapy. Secondary endpoints included overall response rates (ORR), infusion times, serious adverse events (SAE) in induction and maintenance, and rituximab pharmacokinetics in maintenance therapy.Results: Baseline characteristics were: median age 57y (33.3% ≥60y); 40.2% female; ECOG performance status 0: 70.6%; Ann Arbor stage III: 28.4% and IV: 71.6%. Serum β2-microglobulin and LDH at baseline were above normal in 66.3% and 20.6%, respectively. CR/CRu at the end of induction in 102 patients was 51.0% (ORR 86.3%). 1% had progressive disease (PD) during induction. 2 subjects died during the induction period, both due to SAEs (probable pulmonary embolus, acute respiratory distress). SAEs occurred in 22.5% of subjects during induction with the most common event being febrile neutropenia (7.8%). Grade 3–4 R infusion-related toxicity occurred in 4.9% of patients in cycle 1; this decreased to 1% by cycle 2 of induction. Two subjects discontinued R for infusion-related toxicity. 44% of patients were able to receive their R dose within 3 hrs at cycle 2 and 69.2% of patients at cycle 6.Conclusion: Patients with advanced stage indolent NHL treated in the community setting with R-CHOP induction tolerate therapy well and have an excellent response rate. The outcomes of maintenance therapy and rituximab pharmacokinetics in maintenance await further follow-up.