Anencephaly occurs in 1:1,000 to 1:20,000 infants who are potential donors in pediatric heart transplantation, so it is important to define any morphologic differences between the anencephalic and normal heart in newborns. The dimensions of the heart in anencephalics, however, may differ. For example, the absence of cerebral tissue in anencephalic fetuses may decrease the heart load resulting in a smaller heart. The position of the heart in the thoracic cavity of an anencephalic fetus may affect the size and shape of the heart. This study compares the ventricular volumes and the inlet and outlet lengths of right and left ventricles in 11 normal and 11 anencephalic fetuses of gestational ages between 27 and 35 weeks. There was no statistically significant difference between the right ventricular volumes of normal and anencephalic fetuses, however, the difference between the left ventricular volumes was found to be almost statistically significant (P = 0.07). No statistically significant difference was found between the right and left ventricular volumes of normal fetuses; in anencephalic fetuses left ventricular volumes were found to be significantly smaller than right ventricular volumes (P = 0.05). The outlet length of the right ventricle and the inlet and outlet lengths of left ventricle in anencephalic fetuses were found to be short in comparison with those of normal fetuses (P = 0.01, P = 0.008, P = 0.01). It is proposed that anencephalics, because of these morphologic differences, should be reconsidered as possible donors for heart transplantation. (C) 2004 wiley-Liss, Inc.