Intraoperative neurophysiological monitoring (IONM) is a valuable tool to prevent damage by detecting dysfunction before reaching an irreversible stage in brain, spine and other surgical procedures. This article focuses on the intraoperative application and clinical utility of somatosensory evoked potentials (SEP), motor evoked potentials (tcMEP) and triggered and spontaneous EMG. Somatosensory evoked potential (SEP) monitoring used in several decades helped to prevent neurologic deficits. However, motor compromise can occur without SEP warning and SEP deterioration can occur without motor deficit. Intraoperative MEP monitoring in patients with spinal and cranial lesions is thought to be a valuable tool for prevention of postoperative motor deficits. In recent years, motor evoked potential recording following transcranial electrical stimulation has emerged as a reliable technique to intraoperatively assess the functional integrity of the motor pathways.Spontaneous and triggered EMG is getting widely used as a means of monitoring nerve root function during spine surgery. Although IONM is a valuable technique that provides sensitive and specific indications of neurologic injury, it does have limitations that must be understood. The monitoring team must be well trained, be able to provide the surgeon feedback in real time, and coordinate activities with those of the surgical and anesthesia teams.