The writers of the classic articles on the subject of congenital heart disease, such as Peacock,1Rokitansky,2Rauchfuss,3Keith,4Herxheimer5and Abbott,6have little to say of congenital mitral stenosis more than to mention its rarity or refer to two or three cases. It is said to be more rare than atresia of the mitral orifice, which statement is substantiated by a comparison of the number of cases found in medical literature with those of complete occlusion of the left auriculoventricular passage. Eleven examples have been found established by necropsies, and these, with the case reported here, make an even dozen in all. REPORT OF CASE History. —A girl, white, born, Aug. 5, 1917, at full term, after a normal and easy labor of five hours' duration, weighed 7 pounds (3.2 kg.). The father was 27, the mother, 26, and both were in good