Twenty-three patients with the clinical diagnosis of possible multiple sclerosis (MS) were tested with magnetic resonance imaging (MRI) and trimodal evoked potentials. Fourteen patients showed abnormalities on both MRI scans and at least one evoked potential modality (65%). Four patients had normal MRI scans but at least one abnormality on evoked potential testing (17%). One patient had normal triple evoked potentials with an abnormal MRI result. Four patients had normal results on both MRI and triple evoked potential testing; two of these patients were later found to have immunologic abnormalities in the cerebrospinal fluid consistent with the diagnosis of MS. Combined evoked potential testing was found to have a higher sensitivity than MRI in confirming a diagnosis of MS. Three patients with the clinical diagnosis of definite MS were also tested. All these patients showed abnormalities on evoked potential testing, although one patient had a normal MRI result. Of all 26 patients who were studied, 17 showed abnormal MRI results and 21 showed at least one abnormality on evoked potential testing.