Clinical neurophysiology encompasses a variety of diagnostic tests including EEG, nerve conduction studies, electromyography, evoked potentials and polysomnography. This chapter describes the tests that are most widely used for monitoring during neuroanaesthesia and neurocritical care, specifically, EEG, somatosensory evoked potentials (SSEPs), brainstem auditory evoked potentials, motor evoked potentials (MEPs) and electromyography (EMG). The main indications for EEG are in the diagnosis and management of epilepsy, sleep studies and neuromonitoring. Evoked potentials are the electrical response from the nervous system to an external stimulus. There are two types of EPs: sensory and motor. SSEPs monitor the integrity of sensory pathways, including peripheral nerves, and MEPs the motor pathways. Electromyography is a technique used to evaluate the electrical activity in muscle fibres. Two types of EMG monitoring commonly used include: recording spontaneous electrical activity and recording responses generated by stimulation of motor nerves.