From 1957 to 1985, 842 patients were diagnosed as having thoracic hydatid cysts; 810 cysts were intrathoracic, 29 occurred on the "liver roof," 2 were cardiac, and 1 was on the chest wall. A total of 1,010 surgical procedures were performed in 807 patients (35 refused operation). There was a total operative mortality of 0.6% (5 deaths). Procedures became more conservative as experience was gained, and 79% of the procedures were endocystectomies. Intact endocystectomy (Barrett's technique) without preliminary aspiration was the approach of choice. Careful protection of the operating field, suturing of all the bronchial openings, and capitonnage were the keys to successful treatment. One hundred six patients with intact endocystectomies done before July, 1975, were followed for 3 to 20 years. Ruptures occurred during cyst manipulation in 35 patients (33%). Recurrence after operation was seen in 2 patients (1.9%). There were no deaths among the patients undergoing intact endocystectomy. In comparison, we followed 136 patients who underwent aspiration endocystectomy and the recurrence rate was 3.7% (5 patients).