Patients who noticed worsening of their skin disease after using topical corticosteroid preparations were patch tested both with the commercial preparation and the corticosteroid itself. Between 1987 and 1989, 10 cases of contact dermatitis due to topical corticosteroids were detected in this way. The corticosteroids wee amcinonide (2 patients), hydrocortisone butyrate, clobetasol propionate (2), betamethasone valerate (2), prednicarbate and fluocortolone (2). Patch tests with the commercial preparations and the corticosteroids themselves elicited reactions almost identical in time course and severity. Individual sensitivity seems to be more important for test results than test conditions. 9 of the 10 patients underwent further patch testing with a corticosteroid series. In 2 patients, a true cross-reaction between budesonide and hydrocortisone butyrate was found. All 9 patients showed further sensitivities to other corticosteroids. Most of the cross or concomitant reactions could be categorized into recently defined corticosteroid classes. To improve our understanding of corticosteroid sensitization, and to help the patient avoid reactions to other topical corticosteroids, a corticosteroid series should be patch tested in every case of corticosteroid sensitivity.