The chimeric anti-CD20 monoclonal antibody rituximab was recently approved for the treatment of malignant B cell lymphoma. We report the case of a 49 year-old female with advanced mantle cell lymphoma (MCL), who successfully underwent auto-peripheral blood stem cell transplant (auto-PBSCT) in combination with in vivo purging of tumor cells using rituximab. Systemic swelling was detected in her lymph nodes, and she was histologically diagnosed with MCL. From bone marrow involvement and 28% of lymphoma cells in her peripheral blood, she was identified as stage IV of MCL. She achieved a partial response (PR) after three cycles of standard chemotherapy (ProMACE-CytaBOM) followed by 1 course of rituximab at 375 mg/m2 per week for four weeks. Prior to treatment with rituximab, IgH/bcl-1 translocation in her peripheral blood was found to be positive in 0.5% of 199 cells. After administration of rituximab, this fell to 0% in her peripheral blood and bone marrow. Stem cells were mobilized with cyclophosphamide at 2,000 mg/m2 for 2 days, followed by granulocyte colony-stimulating factor (G-CSF). On one day prior to harvest, rituximab was infused at 375 mg/m2 for in vivo purging of tumor cells. The IgH/bcl-1 translocation in the peripheral blood stem cell harvest (PBSCH) product was found to be 0%. Subsequently, a pretreatment regimen of CBDCA at 350 mg/m2 x 4, ETP at 500 mg/m2 x 3, MCNU at 200 mg/m2 x 1, and CPA at 2,000 mg/m2 x 2 was adopted to condition the transplant, followed by auto-PBSCT. After the transplant, the patient achieved an uncertain complete response (CRu). The present case suggests in vivo purging with rituximab is effective, and that this method may have a role as a first-line therapy in MCL patients who respond poorly to standard treatment.