Congenital diverticulosis of the left ventricle is an extremely rare maldevelopment. The following case of sudden or unexpected death is reported because of this finding. REPORT OF A CASE Baby boy S., a full term white male infant, was delivered by low forceps at the Jewish Hospital of Brooklyn at 6 p.m. on Jan. 5, 1947. The mother was a 30 year old primipara whose pregnancy was uneventful. The first stage of labor lasted twelve and one-half hours and the second stage two and one-half hours. The patient had a slightly delayed, weak cry, grunting respirations and moderate cyanosis. The weight at birth was 7 pounds 5 ounces (3,316.9 Gm.). There was moderate molding of the skull but no caput succedaneum or external signs of injury to the scalp or skull. Oxygen and vitamin K subcutaneously were administered. Physical examination two hours after birth revealed a good cry, cyanosis of