Radiation therapy is an extraordinarily effective skin-directed therapy for cutaneous T-cell lymphomas. Lymphocytes are extremely sensitive to radiation and a complete response is generally achieved even with low doses. Radiation therapy has several important roles in the management of mycosis fungoides. For the rare patient with unilesional disease, radiation therapy alone is potentially curative. For patients with more advanced cutaneous disease, radiation therapy to local lesions or to the entire skin can effectively palliate symptomatic disease and provide local disease control. Compared with other skin-directed therapies, radiation therapy is particularly advantageous because it can effectively penetrate and treat thicker plaques and tumors.