Three cases of criss-cross heart which we have observed during last five years are described. All of these cases were diagnosed by angiocardiography and two-dimensional echocardiography, and one of them was verified by autopsy. Two of them are unique among cases reported thus far. Case 1 shows ordinary criss-crossing with supero-inferior ventricle, and case 2, extreme crossing atrioventricular (A-V) valves, in which the right-sided right atrium connects to the left posteriorly positioned right ventricle through the tricuspid valve, and the left-sided left atrium to the right anterior left ventricle via a posteriorly positioned mitral valve. In case 3, the criss-cross appearance is secondary to displacement of the heart by compression caused by a diaphragmatic hernia. Findings in these cases suggest that criss-cross heart is caused not only by primary rotation of the ventricles during cardiac morphogenesiss but also by secondary rotation of a formed heart induced by extracardiac compression. The degree of rotation in these cases revealed a wide spectrum from minimal to extreme. In addition, subxiphoid two-dimensional contrast echocardiography is recommended as the only accurate method of non-invasive diagnosis of this condition.