Pulmonary endometriosis is a rare disease which is characterized by hemoptysis during menstruation (catamenial hemoptysis). We report a case of pulmonary endometriosis in a 33-year-old housewife. She has had regular menses with moderate flow and minimal dysmenorrhea. She had undergone curettage in May 1995 for artificial abortion. In July 1995, she experienced the first episode of hemoptysis. A chest CT scan revealed a 2.0 1.0 cm sized ill-defined soft tissue density in the periphery of anterior segment of the left upper lobe with a surrounding irregular ground-glass opacity. A left upper lobectomy was done under the diagnosis of pulmonary endometriosis. Cut section of the resected lung showed a round red-brownish solid lesion, measuring 2.0x1.0cm in cross. Microscopically a focus of the endometrial tissue, which was composed of endometrial glands and stroma, was found in the lung parenchyme and many hemosiderin laden macrophages were seen in the surrounding alveoli. The postoperative course was favorable with no further episodes of hemoptysis.