In this study, we examined 37 patients with brainstem vascular lesions. We found that brainstem auditory evoked potentials (BAEPs) are completely different in patients with acute rather than chronic vascular lesions in the pons. These data highlight the importance of BAEP follow-up studies and clarify the sites that generate these potentials. In this regard, the lesions limited wave V activity from the inferior colliculus to the rostral pons contralateral to the stimulated ear. On the other hand, the generation site of wave III activity depended on the decussating fibers of the trapezoid body. Moreover, a patient with a pontine hemorrhage clearly demonstrated that generation of wave III activity largely depended on the superior olivary complex contralateral to the stimulated ear. Similarly, wave IV ipsilateral stimulation to the lesion and wave V contralateral stimulation to the lesion were affected by the same discrete lesion at the mid portion of the pons, and the lesion anatomically included the nucleus of the lateral lemniscus. These data suggest that wave IVs are generated by the ipsilateral nucleus of the lateral lemniscus. The pathway of wave V activity likely crosses through Probst's commissure at the level of the mid-pons. We present a schematic illustration of the generation sites and pathways of BAEPs in humans. In this regard, wave I activity was generated by the VIIIth nerve, wave II activity was generated by the cochlear nucleus ipsilateral to the stimulated ear, wave III activity was generated by the superior olivary nucleus contralateral to the stimulated ear, wave IV activity was generated by the ipsilateral nucleus of the lateral lemniscus, and wave V activity was generated by the contralateral inferior colliculus. In addition, we describe the pathways for BAEP generation, the mechanisms that mediate binaural interactions, and the properties of the BAEP generators.