A rare communication between the right pulmonary artery and the left atrium in a 3.5-year-old girl is described. Cyanosis of a central type and a continuous murmur over the heart were presenting symptoms. Echocardiography revealed only excessive pulsations of the pulmonary artery, while catheterization pointed to an abnormal aneurysmal communication between the right pulmonary artery and the left atrium. At this point the O2 saturation was at the level of the left atrium. The communication was clinically classified as a type IV according to Nelson. After an unsuccessful attempt through a right thoracotomy, the ligature of this fistula has been performed in the second attempt through a median sternotomy and under complete extracorporeal circulation. Clinical course and review of literature of this rare anomaly of the heart are being presented.