Thoracoscopic sympathectomy has become the most widely used approach to cervicothoracic sympathectomy. Appropriate selection of cases and a knowledge of the regional anatomy are essential in achieving good clinical results. The physiology and anatomy of the upper thoracic sympathectomy system and the indications, contraindications, and complications of the operation are described. The technique of the operation as done at the University of Virginia is then presented in a step-by-step manner.