Four cases of cor triatriatum are reported in 6 weeks to 23 months old infants. Two were associated with partial anomalous pulmonary venous connection and one with a mild aortic stenosis. Two were successfully operated on and are now normal children: one of these underwent surgery at 3 months with an hemodynamic control one year later. The two others died: the youngest because of an inadequate overloading transfusion, the other soon after pulmonary angiography. Problems in diagnosis and treatment of this rare but very tractable condition are discussed.