Even such traditional treatment modalities in dermatology as tars, anthracene derivatives and UV light are probably immunosuppressive in altering antigenic structures of keratin and interfering with the functions of the Langerhans cells. These are profoundly depleted by phototherapy (UVB) and photochemotherapy (PUVA), modalities which not only can clear up psoriasis, but also improve skin disorders such as contact allergy, mycosis fungoides, acne and urticaria pigmentosa. Cytostatic immunosuppressors like cyclophosphamide, azathioprine, methotrexate, and chlorambucil, combined with systemic steroid therapy, can improve and sometimes induce remission in autoimmune skin diseases with a grave prognosis, such as pemphigus vulgaris, bullous pemphigoid, lupus erythematosus, dermatomyositis, polyarteriitis nodosa and Wegener's granulomatosis. The latter two have also been treated effectively with steroids and sulphapyridine or dapsone. Dapsone, probably in some immunosuppressive way, can clear severe and otherwise resistant cases of acne, when combined with oral tetracycline. Dapsone has a therapeutic effect in some cases of pyoderma gangrenosum and in autoimmune-complex arteritis, and its efficacy in dermatitis herpetiformis is well known. Gold therapy is effective in pemphigus. The therapeutic effect of chloroquine derivatives in discoid lupus erythematosus and polymorphic light eruption may be considered immunosuppressive. Some recently introduced therapeutic approaches based on immunostimulation or immunomodulation are briefly discussed: BCG inoculation in malignant melanoma, induction of contact allergy to DNCB or SADBE (squaric acid dibutylester) in alopecia areata, and levamisole in multiple and persistent virus warts and recurrent herpes. Therapeutic hyposensitization has no place in contact allergy, but 'hardening' may take place in occasional cases by continued low grade contact with the offending allergen. Only rarely does this seem to induce more lasting immunological tolerance.