Of two infants with congenital cardiac diverticula one had a defect consisting of a submitral valvular diverticulum rather than the expected aneurysm. It was clearly shown by echocardiography as well as angiography and was associated with moderate mitral incompetence and a poorly functioning left ventricular wall. The second infant had an isolated apical left ventricular diverticulum with subnormal left ventricular function and severe mitral incompetence. Because of intractable congestive heart failure this infant underwent successful replacement of a dysplastic fibrotic mitral valve which on histological examination had myxomatous features. The association between congenital mitral disease and congenital apical diverticular may be related to race and sex.