The embryology, pathology, clinical picture, and surgical treatment of transposition of the great vessels have been extensively reviewed. Less attention, however, has been given to the anatomy of the chambers of the heart in this condition. One name has been used to describe more than one anatomical type of transposition, or several names (mostly non-descriptive) have been used to describe one anatomical type. Corrected transposition (Rokitansky, 1875;Anderson, Lillehei, and Lester, 1957; and others), reversed torsion of the human heart (Lewis and Abbott, 1915), mirror image transposition of the ventricles, aorta, and pulmonary artery (Beattie, 1922), transposition of the ventricles and the arterial stems (Walmsley, 1931), mixed lhvocardia with transposed ventricles with complete pseudotransposition (Lev, 1954), and inverted transposition (Spitzer, 1923): these are all different terms used to describe one type of corrected transposition of the great vessels. Dextrorotation and 'some type of lkvocardia', were two terms used by de La Cruz, Polansky, and NavarroL6pez (1962) to describe one type of corrected transposition of the great vessels with isolated dextrocardia and isolated levocardia respectively. Whereas the term dextroversion has been used by Grant (1958) to describe one variety of isolated dextrocardia, it has been used by Lichtman (1931) to indicate displacement of the heart to the right by acquired or congenital causes, by Paltauf (1901) and Monckeberg (1924) to signify an extrinsic congenital dextrocardia, and by Harris and Faber (1939) to describe their Case 16 of corrected transposition with l&vocardia. Mixed kavocardia and mixed dextrocardia (Lev, 1954) are two terms that have been used when each atrium is not connected to its corresponding ventricle, in lievocardia and in dextrocardia respectively. The object of this paper is to discuss the basic anatomical types of transposition of the great vessels and to advocate the use of their actual anatomical names. Inversion means a reversal in the frontal plane of the lateral relations between structures, and transposition means a reversal of relations in the antero-posterior plane. The chambers of the heart are best named according to the morphology, and morphology is best recognized by the architecture of the septum (Lev and Rowlatt, 1961). Thus the right atrium presents a limbus and a fossa ovalis on its septal surface; and the left atrium has on its septal surface the irregular configuration of the septum primum as it is adherent to the septum secundum. The right ventricle presents the septal and parietal bands forming the crista supraventricularis, and a trabeculated septum in the inlet. The left ventricle presents a relatively non-trabeculated septal surface in its basilar portion, and a mildly trabeculated apical portion, with the fibres streaming parallel to the outflow of blood.In 1923 Spitzer recognized four grades of transposition of the great vessels. In his type 1, the pulmonary trunk arises from the right ventricle, and the aorta overri...