Extracorporeal photophoresis (ECP), a therapeutic modality that has been under investigation for some years, is based on separation of a leucocyte/lymphocyte-enriched cell fraction from the peripheral blood, extracorporeal treatment of the cells with 8-MOP/UVA and subsequent reinfusion of the cells in the patient. Its main effects seem to consist in changes to the immunologic behaviour of the photoinactivated/modulated cells. The immune response of the host is obviously stimulated by this treatment. ECP is normally performed for 4 h per day on 2 consecutive days every 4 weeks. The treatment is well tolerated and causes few side effects. In our department, 1210 ECP treatments were administered to 41 patients between 1990 and 1994 and a preliminary evaluation was performed. These patients included 21 with cutaneous T-cell lymphoma (CTCL), 10 with progressive systemic scleroderma, 4 with chronic graft-versus-host disease and 1 each with pemphigus vulgaris, epidermolysis bullosa acquisita, lupus erythematosus and cutaneous mucinosis. Patients with erythroderma and preserved immunocompetence achieved the best responses of all patients with CTCL. A treatment combining ECP with rIFN-alpha, PUVA and/or radiation was also successful in patients with tumour-stage CTCL and lymph node involvement. Progressive systemic scleroderma responded in more than 50% of our cases. Treatment results were impressive in 4 patients with chronic graft-versus-host disease presenting with sclerodermatous and lichenoid changes of the skin and mucous membranes. A clear improvement was also observed in the patient with pemphigus vulgaris refractory to standard therapies and in another patient with scleromyxoedema (Arndt-Gottron syndrome). The effectiveness of ECP seems to be quite well established in CTCL, but remains to be examined in autoimmune dermatoses. ECP is an attractive addition to the dermatological therapies available but our experience is still preliminary.