OBJECTIVES: The morphologically right and left ventricles are distinguished from each other based on their internal anatomical features, because their external (epicardial) surfaces do not appear to have any distinguishing mark for such ventricular identification. Nevertheless, ventricular identification based on epicardial characteristics, if these were possible, would be interesting to surgeons, because this would enable them to identify each ventricle rapidly upon opening the chest. This made us curious as to whether or not the two ventricles may be distinguished based on their epicardial coronary arterial patterns, because this is the most obvious epicardial ventricular feature. METHODS: This idea led us to formulate the following 2 hypotheses: (i) The morphologically left ventricle is always the one that receives the higher number of the marginal arteries as compared to the morphologically right ventricle. (ii) Only the morphologically left ventricle receives the diagonal arteries from the anterior and posterior interventricular arteries. These hypotheses were tested in this anatomical observational study by examination of 98 normal and 398 congenitally malformed formaldehyde-preserved hearts encompassing most malformations, including rare ones and hearts in which 1 ventricle is hypoplastic. RESULTS: These examinations show that both hypotheses are false. CONCLUSIONS: The two ventricles cannot be distinguished from each other based on the number of marginal arteries that they receive or which one receives diagonal arteries; both ventricles may receive diagonal arteries from either or both interventricular arteries.