Nerve conduction and needle examination interpretation requires knowledge of normal values and understanding the significance of variations from normal. Abnormalities can help diagnose a focal neuropathy, distinguish a demyelinating neuropathy from axonal neuropathy, and detect a myopathic process. This chapter discusses nerve conduction study interpretation. Nerve conductions can be used to determine if the lesion is distal, proximal, or segmental. Amplitude can be used to determine if axon loss, conduction block, or both are present along a nerve segment. Nerve conductions can help determine if the lesion is neuropathic or myopathic. After nerve injury, motor axons may remain excitable for up to 7 days, and sensory axons may remain excitable for up to 11 days. There are four components of needle electromyography that are used to guide interpretation: insertional activity, motor unit morphology, motor unit recruitment, and pattern of muscle abnormalities.