Cysts of the thoracic duct are rare. We report a case of a cervical thoracic duct cyst and review 29 thoracic duct cysts reported previously (19 mediastinal, 9 cervical, and 1 abdominal). The mean age of the patients was 47.6 years (range 17 to 86 years). Fourteen (46.7%) of the patients were asymptomatic. When symptoms were present, they ranged from retrosternal pain, dysphagia, and dyspnea to respiratory insufficiency and superior vena cava compression. Diagnosis of the cyst can be made after computed tomography or ultrasonography. The cystic fluid contains T lymphocytes and triglycerides in excess. The symptoms in a patient with a thoracic duct cyst are related to compression of adjacent structures. The most profound symptoms are likely to be produced by mediastinal cysts above the aortic arch. Treatment consists of surgical removal of the cyst and ligation of all lymphatics connected to the cyst.