A 35-year-old primigravida was admitted to the Department of obstetrics complaining of dyspnea and left back pain at 21 weeks' gestation. Chest roentgenogram revealed diffuse reticulonodular shadows predominantly in both lower lung fields and arterial hypoxemia was present. Pulmonary function tests showed restrictive impairment and decreased carbon monoxide diffuse capacity. From these results, interstitial pneumonia was suspected and she was first treated with prednisolone. However during her pregnancy, spontaneous pneumothorax occurred. Following spontaneous delivery of healthy infant at 37 weeks, left chylothorax occurred, and pleurodesis was performed with OK432. Thereafter the histological diagnosis of pulmonary lymphangiomyomatosis was made by transbronchial lung biopsy and treatment of prednisolone was stopped. She was treated with tamoxifen. In addition, progesterone-receptor was detected in the pulmonary tissue obtained at open lung biopsy. She was treated with cyclophosphamide in addition to tamoxifen. At present, shortness of breath has decreased slightly in comparison with one year previously, but no improvement has been seen in lung function tests or chest roentgenogram.