Objectives: To evaluate the frequencies, clinical characteristics, and outcomes of catamenial and endometriosis-related pneumothoraces occurring in women with no underlying lung disease referred for surgical treatment. Methods: Clinical files of all the women of reproductive age referred to our center during a 6-year period for surgical treatment of spontaneous pneumothorax were retrospectively reviewed. Catamenial pneumothorax was defined as recurrent pneumothorax occurring between the day before and within 72 hours after the onset of menses. All histological slides were reviewed to confirm initial diagnoses. Results: One-hundred and fourteen women underwent video-assisted thoracic surgery. Twenty-eight women (24.6%) had catamenial pneumothorax (right-sided in all but one) and diaphragmatic abnormalities (perforations and/or nodules) were observed in 22 of them. Diaphragmatic abnormalities were seen in 21/86 patients with non catamenial pneumothorax. Histological examination found endometriosis, mainly diaphragmatic, in 18/28 catamenial and 11/86 non catamenial pneumothoraces. A 6-month antigonadotropic treatment was prescribed postoperatively to women with either catamenial or endometriosis-related pneumothorax. Mean follow-up was 32.7±18.5 months. Recurrence rates in catamenial, non catamenial but endometriosis-related, and non-catamenial non endometriosis-related pneumothoraces were 32, 27, and 5.3%, respectively. Conclusions: Our experience shows that 1) catamenial and/or endometriosis-related pneumothoraces account for an important percentage of spontaneous pneumothoraces referred for surgery; 2) diaphragmatic abnormalities seem to play a fundamental role in their pathogenesis; 3) management is difficult because of the high recurrence rate.