We conducted a multicenter, phase II trial to investigate the efficacy and safety of rituximab plus CVP (R-CVP) combination therapy for patients with previously untreated stage III or IV marginal zone lymphoma (MZL). The treatment consisted of rituximab 375 mg/m(2), cyclophosphamide 750 mg/m(2) and vincristine 1.4 mg/m(2) (maximum 2.0 mg) being given intravenously on day 1 and oral prednisolone 100 mg on days 1-5. The treatment was repeated every 3 weeks and this was continued for six or eight cycles. Forty-two patients were enrolled from 13 institutes in Korea. Among them, two patients were dropped after the first and second cycles of chemotherapy, respectively, without evaluation. The 40 patients received a total of 287 cycles of R-CVP chemotherapy. The overall response rate was 88% (95% CI, 77-98%) with 24 complete responses (60%). The median duration of response was 28.3 months. After a median follow-up of 38.2 months, the estimated 3-year progression-free survival and overall survival were 59% and 95%, respectively. There were 30/287 cycles (11%) and 5/287 cycles (2%) of grade 3 or 4 neutropenia and febrile neutropenia, respectively. The R-CVP regimen can be an effective and tolerable first-line immunochemotherapy regimen for advanced stage MZL.