The use of high-dose electron-beam therapy for mycosis fungoides at Stanford University is reviewed. Since 1966, 140 patients have been treated in this fashion. Their clinical characteristics including initial extent of disease are reviewed. The results of routine staging studies are examined. Eighty-four percent of the patients achieved an initial complete remission; this was inversely related to the initial extent of skin involvement. The overall survival rate was 46% at 10 years with the major prognostic factor being the initial extent of skin involvement. Other factors which had an influence on the patient's progrnosis included the presence of palpable adenopathy, the patient's age, the achieving of an initial complete remission, the initial dose of electron-beam therapy, and the treatment with adjuvant topical mechlorethamine. The development of a rationale for the treatment of patients with all stages of mycosis fungoides based upon these clincal observations is discussed.