A total of 115 patients with mycosis fungoides were given total-skin electron-beam therapy (TSEB), utilizing 3.5-mev electrons at doses of 400 rads to the entire skin surface once a week for 6--8 consecutive weeks. Prompt relief of symptoms and regression of lesions were observed in all patients. Of the 81 patients at risk for 12--91 months (median, 24 months) following TSEB, initial unmaintained remission lasted 6--69 months (median, 19 months). No untoward immediate or late effects have been noted in the bone marrow or normal skin which was irradiated. The duration of remission following TSEB correlated well with lymphocyte responsiveness to various mitogens and antigens, but not with the initial response. Thymic hormone factor levels (Facteur Thymic Serique) were elevated in the majority of these patients with mycosis fungoides.