A 48-year-old woman hospitalized because of spontaneous pneumothorax. She suffered dyspnea since three years before. Diffuse reticulonodular interstitial pattern was observed in the radiography. The transbronchial biopsy suggested lymphangioleiomyomatosis, the diagnosis being supported by open pulmonary biopsy. Usefulness of transbronchial biopsy is discussed and several treatment modalities are described.