The introduction of corticosteroids into oral medicine heralded a therapeutic advance, and substantial benefits have occurred from their use. Three topical steroids are being used currently in oral diseases, i.e. hydrocortisone hemisuccinate, triamcinolone in Orabase 0-1 per cent and betamethasone valerate 0-1 mg. The efficacy of these agents can be increased markedly if they are administered during the prodromal phase of ulceration, i.e. when lymphocyte activity is at its maximum. Therapeutic doses of all of them can be exceeded three times without impairing adrenal function. Nevertheless some of these preparations, as exemplified by topical medication, induced an unfortunate acute pseudomembranous candidiasis without any alteration in the plasma cortisol level. The routine examination and treatment of ulcers in the mouth should be a careful exercise helped by a good light source and a tongue spatula. Oral lesions affecting the soft tissues may be often difficult to diagnose, because of the rapid occurrence of secondary changes, such as maceration from moisture, abrasion by food and teeth, perhaps, and the existence of erosions and ulcerations from ruptured vesicles or bullae. Thus, diagnosis will depend not only on the grouping and distribution of lesion, but also on its subsequent behaviour. In some cases too there will be associated changes in the facial skin or elsewhere in the body.