Examination by magnetic resonance imaging (MRI), evoked potentials (EP) and cerebrospinal fluid (CSF) analyses was carried out on 97 definite, 20 probable and 40 possible multiple sclerosis (MS) patients (McAlpine’s clinical criteria). MRI of only 4 transverse brain sections at the level of the ventricles and the analysis of the first 4 echoes showed periventricular or parenchymal lesions, or both, in 114 of the 117 definite and probable MS patients and in 25 of the possible MS patients. MRI was more sensitive than the CSF analyses or EP. The MRI abnormalities were not, however, MS-specifi