Hydatid disease remains a serious health problem for the Mediterranean countries, such as Turkey. Living in a rural area is an important risk factor for the disease. Hydatid cysts are usually located in the liver, lung, and brain. Mediastinal hydatid disease is very rare that have been only anecdotally in the literature. The objective of this study was to evaluate the clinical and radiographic findings and surgical treatment of this unusual lesion. Between 1985 and 2002, 11 cases with primary mediastinal hydatid cyst were treated surgically at our clinic. Median age was 28.4 and ranged from 19 to 46 years. Symptoms included chest pain in nine patients (82%), and cough in six patients (54%). The cyst was located in the anterior mediastinum in four patients (36%), in the posterior mediastinum in live patients (45%) and in the middle mediastinum in two patients (18%). All cysts were intact except one cyst that ruptured into right intrapleural space. Surgical approach was right thoracotomy in five patients (45%), left thoracotomy in three patients (27%), and median sternotomy in three patients (27%). Total pericystectomy was chosen as the surgical procedure in all patients except four (36%), who had cystectomy and local curettage for cyst located vital structures. There were no complications and mortality postoperatively. Primary hydatid cysts of the mediastinum are distinct clinical entity that must be considered when caring for a patient with a mediastinal mass in endemic regions. Because of surrounding vital structures the cyst should be treated without delay. (C) 2002 Elsevier Science B.V. All rights reserved.