The My7 antigen that is expressed on the basal cells in normal skin and inflammatory disorders is absent in the lesions of cutaneous T-cell lymphoma (CTCL). Induction of My7 expression in basal cells in the cutaneous lesions of 12 patients with mycosis fungoides and three with Sézary syndrome treated with interferon-alpha 2a (IFN-alpha 2a) for 10 months was investigated. Biopsies were taken from the same area before treatment and after 2, 6 and 10 months of therapy with IFN-alpha 2a. My7 antigen was expressed on the basal cells only in those patients who showed either a complete or partial response to therapy with IFN-alpha 2a.