The evaluation of patients with suspected lumbar radiculopathy is one of the most common reasons patients are referred for electrodiagnostic testing. The utility of this study depends on the expertise of the physician who plans, performs, and completes the study. This article reviews the strengths and weaknesses of electrodiagnosis to make this diagnosis, as well as the clinical reasoning of appropriate study planning. The current use of electrodiagnostic testing to determine prognosis and treatment outcomes is also discussed.