Visual, somatosensory and brain stem auditory evoked potentials were recorded in 84 patients in whom the diagnosis of multiple sclerosis was under consideration. The patients were followed up for a maximum of 38 months or until a definite diagnosis of multiple sclerosis or of some other condition was established. Seven patients were found not to have multiple sclerosis. Abnormal evoked potentials indicating clinically silent lesions were found at the initial investigation in fourteen of the twenty-eight patients in whom a diagnosis of clinically definite multiple sclerosis was accepted during the period of follow up. In the thirty-seven patients in whom no change in clinical category occurred during the period such abnormalities were found in five. The visual evoked potential was found to be of greatest predictive value.