Two hundred patients with generalized cutaneous mycosis fungoides were treated with total skin electron irradiation (TSEI) in the Lahey Clinic Radiotherapy Department-MIT High Voltage Research Laboratory between 1964 and 1973. None of the patients had any clinical evidence of extracutaneous disease at presentation. The 3-year absolute survival rate was 54% (107 patients). Analysis of these 107 long-term survivors evaluated the relation between incidence of generalized cutaneous recurrence and total treatment dose given during the initial course of TSEI. Results indicated that in patients with erythroderma, the need for a second course of TSEI was inversely related to the total dose given during the first course. However, the curve seemed to flatten at about 1,500 cGy (rad). In plaque disease, the percentage of patients who received repeated courses of TSEI seemed to be relatively constant independent of total dose given during the initial course (65%-80%). In patients with tumor lesions, the incidence of generalized cutaneous recurrence was directly proportional to total dose. The optimal dose of TSEI for patients with mycosis fungoides may vary depending on types of skin lesions. Total dose during the initial course of TSEI should be kept relatively conservative, particularly in patients with generalized plaques where relapse rate is high allowing reserve of normal tissue tolerance for further TSEI when indicated.