Electrodiagnosis is a quantitative electrophysiologic test that may identify and localize the site of neurologic dysfunction and detect subclinical changes and compensatory processes. Electrodiagnostic (EDX) studies useful in evaluating the peripheral nervous system and spinal cord include electromyography (EMG), nerve conduction studies, and somatosensory evoked potentials. The primary uses of these tests are to evaluate radiculopathy, entrapment neuropathy, or other peripheral nerve study, and results must be presented completely, concisely, and in a standardized format understandable to nonelectromyographers (who may include adjusters, attorneys, hearing officers, and judges with varying degrees of knowledge about clinical neurology). Needle EMG remains the most sensitive electrophysiologic test for determining radiculopathy. Any EDX report should contain the fundamental test results and a summary of the findings and should make clear when facts other than neurophysiological data are included. Reports must be internally consistent to avoid compromising the report's integrity. Errors of fact and technique, incomplete or irrelevant data, and over-, mis-, and underinterpretation of data are too frequent in EMG reports. EDX studies objectively define peripheral nerve injuries, entrapment neuropathies, and radiculopathies; the findings must be clearly presented with supportable conclusions. Carpal tunnel syndrome practice parameters from the American Academy of Neurology and the American Academy of Physical Medicine and Rehabilitation are provided.