Carpal tunnel syndrome (CTS) is a common median nerve compression syndrome and the most common peripheral mononeuropathy. The clinical syndrome is diagnosed by history and physical examination. Electrodiagnostic testing is the objective method used to measure median nerve dysfunction at the wrist and confirm the clinical diagnosis of CTS. Neuromuscular ultrasound imaging of the carpal tunnel provides supportive diagnostic information by revealing pathologic nerve swelling in CTS, and other anatomic anomalies that compress the median nerve. These tests cannot be used to make the diagnosis in the absence of history that includes CTS symptom criteria and excludes other causes.