30 patients with acute exacerbations of multiple sclerosis were treated by ACTH, dexamethasone or methylprednisolone in a double-blind randomized study. Clinical parameters were assessed; cerebrospinal fluid and neurophysiological parameters (visual- and brainstem-evoked potentials) were evaluated at the beginning and at the end of treatment. Dexamethasone was more effective than ACTH and 6-methylprednisolone in shortening bout duration. Neither CSF nor neurophysiological parameters were significantly affected by therapy.