Congenital cysts of the mediastinum are rare, but interesting lesions. Such cysts are important because they may produce distressing symptoms and because some have a malignant potential. Mediastinal cysts of foregut origin represent an important diagnostic group. Classified according to their anomalous embryonic origins they include pericardial, bronchogenic, esophageal, enteric, and nonspecific cysts. A series of 11 consecutive surgically treated cases from the Dep. of Thoracic & Cardiovascular Surgery in National Medical Center from Oct. 1959 to Dec. 1990, all successfully resolved without mortality. The 8 bronchogenic, 1 enteric, & 2 non specific cysts are included in this series. And 2 of 11 were asymptomatic patients presented. The clinical & pathological behavior of the individual cysts comprise a wide variety of patterns. Proper utilization of the many diagnostic tests available can accurately characterize the cysts. The exact histologic diagnosis, however, is rarely made prior to operation.