Currently no standard treatment exists for patients with posttransplant lymphoproliferative disorders relapsed or refractory to chemotherapy after failure of reduction in immunosuppression. We have analyzed the effects of single-agent rituximab treatment in eight patients (seven adult, one pediatric) in this setting. Three patients had been salvaged with rituximab several times. In the seven adults, rituximab salvage therapy achieved complete remission (CR) in three patients (43%) and partial remission in one (14%). In the pediatric patient, a PR was obtained that could be reinduced on relapse with repeated administrations of rituximab. Patients achieving CR either remained in CR or were successfully salvaged again with single-agent rituximab. At a median follow-up of 69 months, median progression-free survival was 9 months and no relevant therapy-associated toxicity was observed. Single-agent rituximab salvage therapy is an effective treatment option in this setting of intensively pretreated patients, with virtually no therapy-associated toxicity.