Mediastinal B-cell lymphomas (with or without sclerosis) have been recently recognized as an entity with particular clinical features. We report 26 patients with a mediastinal large B-cell lymphoma. They represent 5% of the patients with aggressive non-Hodgkin's lymphoma and 2% of all non-Hodgkin's lymphoma seen in our centre between 1962 and 1990. They include 19 females (73%) and 7 males (27%). The sex ratio was 2.7 and the median age was 44 years (range: 17-84 years). Compressive symptoms in relation with a bulky mediastinum were present in 21 cases (80%) and with B symptoms in 5 cases. All these patients received 2 to 4 cycles of chemotherapy with a CHOP-like protocol (epirubicin or doxorubicin, cyclophosphamide, vincristine and prednisone) followed in 24 cases by mediastinum irradiation (40 Gy). Two patients progressed during chemotherapy and did not receive radiotherapy. Nineteen patients had a consolidation chemotherapy according to the same protocol. Twenty-one patients achieved a complete remission after chemotherapy or radiotherapy and 5 failed. Two patients relapsed at 10 months and 9 years. Seventeen patients are alive and in first complete remission with a median follow-up of 102 months (range: 60-260 months). Using the Kaplan-Meier method, the overall survival at 5 and 10 years was respectively 77 and 61% and the relapse-free survival was respectively 68 and 57%. These results confirm the previous findings concerning this distinct entity which is characterized by a predilection for young women, compressive symptoms, a slow response to treatment and a rather good prognosis.