Bilateral catamenial pneumothorax occurred in a 32-year-old parous woman. The 41 previously reported cases of catamenial pneumothorax occurred on the right side. This patient was treated with left-sided pleurodesis and, subsequently, with hysterectomy and bilateral salpingo-oophorectomy. The pathologic mechanism of this peculiar syndrome has been attributed to reflux of air via the genitalia and fenestrations in the diaphragm, menstrual shedding of endometrial cells growing in the visceral pleura, or, possibly, aveolar tissue damage secondary to vascular and bronchiolar spasm resulting from dinoprost tromethamine released from menstrual debris. Treatment needs to be tailored to fit the individual patient's specific pelvic and intrathoracic pathology and procreative desires.