Multiple Sclerosis (MS) is the most frequent chronic neurologic pathology diagnosed in young adults. The demyelinating process leads to axonal myelin loss, causing axonal and glial neuronal dysfunctions, clinically manifested by relapse. Transcranial magnetic stimulation (TMS) is a noninvasive method useful in assessing corticospinal tract dysfunctions in Multiple Sclerosis patients, by recording the prolonged central motor conduction time (CMCT), the increase of the motor threshold and also the reduction in amplitude of the motor evoked potential (MEP). Thus, stimulating the cortical motor area will determine a recordable response characteristic for the electrophysiological behavior of the pyramidal tract. We investigated 37 MS patients with relapse, manifesting by motor defi cit, performing TMS prior to receiving corticosteroids (1000 mg intravenous Methylprednisolone daily, for 5 days), 5 days afterwards and also after one month from the treatment. 26 patients presented both electrophysiological and clinical improvement after therapy, whereas 11 patients did not show any electrophysiological improvement, in spite of a slight amelioration of the symptoms. TMS proves to be a sensitive tool for investigating the relapse and the corticotherapy efficiency.