Normally, the foramen ovale ceases to function after the establishment of respiration, and is actually closed by adhesions at about the tenth day after birth. However, a widely patent foramen is a fairly common congenital lesion, and about 30 per cent of all adult hearts permit the passage of a probe between the two auricles. Distinctly pathologic and extremely rare is the intra-uterine occlusion of the foramen ovale. A few authentic cases have been described by reliable observers. Vieussens1recorded the first case in 1715; since then Smith,2Vernon,3Tait4and Osler5have each reported a case. The first three of the foregoing cases were assembled by Peacock6in 1858 in his monograph on congenital cardiac disease. Most other authors have omitted discussion of this lesion or dismissed it with but few words. Because of its rarity, therefore, the following case is reported: History.