In a review of the literature, I am unable to find a report of any case of congenital cystic disease of the lungs diagnosed clinically before 1925. In that year, Koontz1reported a case and was able to collect 108 other cases. These were all from the European literature and all were based on material obtained at necropsy. This article is to a large extent responsible for the increased interest in, and increased clinical knowledge of, the condition existing today. Since the time this paper was published, I have been able, from the American and English literature, to collect twenty-three reports of cases exclusive of those reported in this series. I presume there are more. Of the twenty-three cases, a clinical diagnosis was made in sixteen and a diagnosis based on material obtained at necropsy in seven. In one case, the clinical diagnosis was confirmed at necropsy. Some authors