Background. We present our experience with thoracoscopic resection of mediastinal bronchogenic cysts in adults. Methods. From November 1990 to September 1993, 20 patients with mediastinal bronchogenic cysts were operated on by thoracoscopy. The average cyst size was 4.9 cm, and the largest diameter was 10 cm. Ten cysts were located in the middle mediastinum and 10 in the posterior mediastinum. Two cysts were complicated. Results. Thirteen bronchogenic cysts were resected completely by thoracoscopy. We had to convert thoracoscopy into thoracotomy because of bleeding in two cases and because of major adhesions to vital structures in five cases. There were no operative deaths and no postoperative complications. Mean hospital stay was significantly less in the completely thoracoscopically treated group. Long- term follow-up (range, 4.5 to 7.5 years) showed no late complications and no recurrence. Conclusions. Preoperative complications, intraoperative injuries, and major adhesions to vital structures seem to be the only unfavorable conditions to thoracoscopic treatment of bronchogenic cysts. This study found encouraging results for thoracoscopic excision of mediastinal bronchogenic cysts in selected patients. (C) 2000 The Society of Thoracic Surgeons.