RELEVANCE. The problem of treating thoracic endometriosis complicated by recurrent spontaneous catamenial pneumothorax is associated with the widespread prevalence of endometriosis, the complexity of its treatment and unsatisfactory long-term outcomes. The diagnosis of catamenial pneumothorax can only be established with a carefully collected history and confirmation of its recurrent nature. Favorable results are achieved with complex therapy carried out by the thoracic surgeon and gynecologist, consisting of an adequate volume of surgical intervention and hormonal therapy with gonadotropin releasing hormone agonists.AIM OF STUDY. To improve the diagnosis of thoracic endometriosis and recurrent catamenial and endometriosis-related spontaneous pneumothorax. To optimize the currently available treatment tactics by reducing the incidence of early relapses of catamenial pneumothorax and creating favorable conditions for the formation of reliable pleurodesis.MATERIAL AND METHODS. We studied the immediate outcomes of complex treatment of 30 patients (14.7%) with right-sided recurrent catamenial (28) and endometriosis-related spontaneous pneumothorax (2), with a median age of 41 (37;44) years, for the period from 2011 to the first half of 2023. Surgical treatment via video-assisted thoracoscopic access was performed in 26 patients (86.7%). After surgery, all the patients were recommended a six-month course of hormonal therapy with gonadotropin releasing hormone agonists.RESULTS. Various types of mechanical pleurodesis were performed in 25 patients (96.1%), resection of the diaphragm — in 17 (65.4%), alloplastic reconstruction with a synthetic mesh implant — in 12 patients (46.1%), pulmonary resection — in 9 (34.6%). In 12 of 26 patients (46.1%) in the early postoperative period, 6 (3; 6.75) days after surgery, a recurrence of catamenial pneumothorax developed, which subsequently required repeated interventions. In 5 patients, the relapse clearly coincided with the menstrual cycle. Early recurrence of pneumothorax required repeated drainage of the pleural cavity in all the patients, chemical pleurodesis in 2, and prolonged drainage of the pleural cavity in 1.CONCLUSION. Surgeries involving resection and reconstruction of the diaphragm with a mesh implant, pleurectomy, lung resection do not ensure the removal of all endometrioid heterotopias of the diaphragm and lung, therefore, during the first mensis after surgery, in the early postoperative period, 46.1% of the patients had a recurrence of catamenial pneumothorax, with no formed pleurodesis, which contributes to the possibility of further recurrences of pneumothorax. Improving the immediate outcomes of complex treatment of catamenial pneumothorax is possible with the preventive administration of hormonal therapy 1.5–2 months before the planned surgical intervention, which requires a multidisciplinary approach of the thoracic surgeon and gynecologist.