Despite the current use of several different methods for diagnosis and follow-up of cerebral vasospasm after subarachnoid hemorrhage, an easy, quick, reliable, and noninvasive method is still needed for evaluation of this entity. We investigated the value of transcranial magnetically evoked motor potential changes during the vasospasm period in a rabbit experimental subarachnoid hemorrhage model. We also recorded motor evoked potential changes after deferoxamine treatment during vasospasm. Our results reveal a significant increase in latency periods of evoked potentials during the angiographically proven vasospasm period (34.5%) over those in sham-operated rabbits (9.5%). With deferoxamine treatment, only a minor increase in latency periods (4.5%) was detected after subarachnoid hemorrhage. These results suggest the potential value of evoked motor potential recording as a diagnostic tool in cases of cerebral vasospasm.