Information regarding rituximab monotherapy with eight weekly infusions for relapsed or refractory indolent B cell non-Hodgkin lymphoma (B-NHL), in particular for patients pretreated with rituximab, is limited. To evaluate the efficacy and safety of eight doses of rituximab monotherapy, 52 patients with relapsed or refractory indolent B-NHL were enrolled in the present study. Forty of 45 eligible patients (89%) had follicular lymphoma and 24 (53%) were at intermediate or high risk group according to the Follicular Lymphoma International Prognostic Index. The median number of prior chemotherapy regimens was 1 (range 1–7). At the median follow-up of 12.2 months, the overall response rate (ORR), complete response rate (%CR), and median progression-free survival (PFS) were 69% (95% confidence interval [CI] 53%–82%), 47% (95% CI 32%–62%), and 15.6 months (95% CI 10.6– months), respectively. In the 33 patients pretreated with rituximab, the ORR, %CR, and median PFS were inferior compared with values for the 12 patients who had not received rituximab previously (64%vs 83% for ORR; 39%vs 67% for %CR; and 13.8 vs 17.5 months for median PFS, respectively). All mild-to-moderate infusion-related toxicities were reversible. Grade 3/4 non-hematologic adverse events occurred in six of the 52 patients. Two patients developed Grade 4 late-onset neutropenia and a decrease (>50%) in serum immunoglobulin was observed in six patients. In conclusion, rituximab monotherapy with eight weekly infusions is effective in relapsed patients with indolent B-NHL, with acceptable toxicities, including in patients pretreated with rituximab; however, careful monitoring is recommended for infections associated with late-onset neutropenia and hypogammaglobulinemia. (University Hospital Medical Information Network no. UMIN000002974.) (Cancer Sci 2011; 102: 1698–1705)