Lymphomatoid granulomatosis is a rare Epstein-Barr virus (EBV)-positive-B-cell lymphoproliferative disorder. Treatment options include corticosteroids, antiviral therapy, interferon-alpha and chemotherapy. However, long-term prognosis is poor and no therapeutic standard has been established yet. In a 21-year-old woman, a biopsy of mediastinal mass revealed lymphomatoid granulomatosis. Combined therapy with valganciclovir and interferon-alpha proved ineffective. In view of the CD20 expression of the tumor cells, monotherapy with rituximab was intiated. After 3 months a complete remission was achieved. Rituximab was continued for another 6 months with subsequent consolidation radiotherapy. This is the first report of an enduring complete remission (20 months) of a non-CNS lymphomatoid granulomatosis treated with rituximab.