Pulmonary lymphangiomyomatosis is a rare but distinct condition caused by progressive widespread smooth muscle proliferation in the perilymphatic regions throughout the lung. The disease is clinically manifested by recurrent chylous pleural effusion, pneumothoraxor ascites and striking female sex predominance. A relationship is noted between lymphangiomyomatosis and certain secondary lesions associated with tuberous sclerosis. The authors experienced a case of pulmonary lymphangiomyomatosis in 23 years old female patient who had been suffered due to recurrent pneumothorax for two weeks. During explorative thoracotomy, a huge cystic mass, 18.5×8.0×3.0 cm can and weighing 100gm, was noted in the lower lobe of the right lung. The external surface was tan brown and dirty with rubbery consistency. The inner surface was also tan brown and dirty with fibrous meshwork. Microscopically, there were varying sized cysts lined by flattened cuboidal cells. There were irregular and nodular proliferation of smooth muscle bundles in the wall of the cysts.