The authors report on 5 cases of diffuse pulmonary lymphangiomyomatosis. This disease occurs in women during the period of genital activity and usually presents with pulmonary signs (9/10) : dyspnoea, pneumothorax, pleural effusion, and hemoptysis. It is also found in association with renal angiomyolipomas and uterine fibromyolipomas. X-ray films of the lungs show : an interstitial syndrome, gas or fluid pleural effusions, and thoracic distention. None of these signs is constant, but the association of an interstitial syndrome with thoracic distention in a young woman appears to be specific for this affection.