A case of pulmonary lymphangiomyoma in a 40-year-old woman is presented. This rare pulmonary disorder is ostensibly unrelated to tuberous sclerosis, another rare disorder with pulmonary manifestations and with fundamentally identical histologic features. From a review of the world literature, it was concluded that the 2 entities are etiologically related. Evidence for the overlap between the 2 disorders includes relevant genetic studies that explain why a familial history of tuberous sclerosis is not elicitable in patients with pulmonary lymphangiomyoma, the discovery that clinically detectable renal angiomyolipomas represent the most important link in establishing a common etiology, the fact that both occur almost exclusively in females, and identical histologic features.