The complex neuroanatomy of the brainstem and the additional distortion incurred by intrinsic lesions have previously discouraged aggressive neurosurgical procedures. Safe access to the brainstem and complete lesionectomy has been thwarted by considerable perioperative risk. Brainstem mapping has established itself as one of the means by which modern neurosurgery can improve surgical outcome while decreasing morbidity. It involves the use of neurophysiologic techniques for the identification of critical structures, such as the cranial motor nuclei and their nerves, and the corticobulbar and corticospinal tracts at different stages of the operation. Familiarity with these techniques can map a safe corridor toward a brainstem lesion and guide the surgeon during the resection. By means of reviewing the available literature, we discuss the anatomic, pathophysiologic, technical, and interpretational aspects of brainstem mapping and elaborate on its indications, limitations, and future directions.