We report the clinical findings of 21 consecutive patients affected by mediastinal large B-cell lymphoma with sclerosis. This type of lymphoma is a recently described histopathologic entity characterized on clinical grounds by distinctive features, which, according to our series, can be summarized as follows: young age (median, 30 years; range, 15 to 42 years), prevalence of females over males (15 v six), rare occurrence of superficial lymph node enlargement (three of 21 patients), and involvement of unusual extranodal sites (kidney six, adrenal cortex two patients). The clinical course appears to be closely related to treatment. In fact, complete remission (CR) was not obtained in the six patients submitted to conventional cyclophosphamide, doxorubicin, vincristine, and prednisone (CHOP) or CHOP plus bleomycin (CHOP-Bleo) regimens until 1985, as opposed to 13 CRs reached in the 15 patients subsequently treated with more aggressive regimens after 1985 (methotrexate with leucovorin, doxorubicin, cyclophosphamide, vincristine, prednisone, and bleomycin [MACOP-B], 12 patients; methotrexate, bleomycin, doxorubicin, cyclophosphamide, vincristine, and dexamethasone [M-BACOD], two patients; and vincristine, cyclophosphamide, fluorouracil, cytarabine, doxorubicin, methotrexate, and prednisone [F-MACHOP], one patient; plus involved-field radiotherapy, 10 patients). Among the 13 patients who achieved a CR, only one relapse was observed at 10 months. The median overall survival of complete responders after an observation period of 11 to 69 months has not yet been reached, and the event-free survival curve indicates that 90% of patients who achieve CR may be potentially cured.