Mediastinal large-cell lymphoma with sclerosis (MLCLS) is a distinctive subtype of non-Hodgkin's lymphoma (NHL) with unique clinicopathology aspects and aggressive behavior. Prompt diagnosis and aggressive chemotherapy followed by consolidation radiotherapy may result in long-term survival in the majority of cases. However, a subset of patients do not respond to first-line or salvage treatment and have a poor prognosis. We report here a 27-year-old man with MLCLS resistant to several conventional chemotherapies and to radiotherapy who achieved a very good partial remission after one year's treatment with daily oral cyclophosphamide (100 mg/day). This is the first report of refractory MLCLS with good response to daily oral cyclophosphamide. This case suggests that daily oral monochemotherapy might be beneficial for some patients with mediastinal large-cell lymphoma with sclerosis refractory to conventional intravenous chemotherapies and radiotherapy.