Four cases of crossed atrioventricular connections are described. All of them were diagnosed at cardiac catheterization by angiocardiography and one was examined pathologically. Two possessed situs solitus, one with concordant connections and the other with discordant connections; the other had two situs inversus, both of them with concordant connections. Two had double-outlet right ventricle, one had transposition of the great arteries, and the other had normally related and connected great arteries. These cases have been interpreted as representing abnormal rotation of the ventricles following sepatation. A review of 36 cases previously reported on and our own cases, suggests that most patients have concordant atrioventricular connections. There are many types of ventriculo-arterial connections, the most frequent being transposition of the great arteries. There has not been any case reported with persistent truncus arteriosus. On the basis of atrioventriculo-arterial connections, we propose a classification for this malformation. We discuss the importance of the bulboventricular loop in the type of atrioventricular connections, some clinical implications for the diagnosis, and analyze the value of the rules to localize the ventricles by means of the position of the great arteries.