Radioimmunotherapy of indolent non-Hodgkin lymphoma (NHL) has achieved objective response rates in clinical trials comparable with standard rituximab with cyclophosphamide, doxorubicin, vincristine, and prednisone chemotherapy, but is relatively underused in routine practice. In this article, we report our clinical experience in 142 consecutive patients who received iodine-131 rituximab radioimmunotherapy for low-grade, predominantly follicular, relapsed NHL. Objective response rates of 67%, with complete response (CR) in 50% and median overall survival of 32 months, matched the response rates in a phase 2 clinical trial of (131)I-rituximab radioimmunotherapy and compares favorably with those reported for (131)I-tositumomab or (90)Y-ibritumomab tiuxetan. Progression-free survival was 18 months overall and 32 months in CR or CR-unconfirmed patients. Our patients comprised 107 (75%) follicular lymphoma, 21 (15%) small lymphocytic lymphoma, 6 (4%) mucosa-associated lymphoid tissue/marginal zone lymphoma, and 8 (6%) mantle-cell lymphoma, with median follow-up of 32 months and 8-year overall survival of 48%. Toxicity was limited to hematologic grade 4 neutropenia, occurring in 10% and thrombocytopenia in 6%. There were no episodes of bleeding or infection requiring hospital admission. Radioimmunotherapy with (131)I-rituximab in routine clinical outpatient practice provides cost-effective, safe treatment of relapsed/refractory indolent NHL, with half of patients achieving durable, complete remission with potential for repeat radioimmunotherapy on relapse.