Recent developments have taken place in the diagnosis of cardiovascular disorders in the area of cardiac imaging techniques. From a previous era of imaging by silhouettes (chest roentgenography, fluoroscopy, angiocardiography), we have emerged into an era of imaging by tomographic scanning (echocardiography, radionuclide tomography, computed tomography, magnetic resonance). A basic understanding of tomographic cardiac anatomy is the foundation for proper use and interpretation of these new imaging modalities. The present report provides a description of the techniques of tomographic cutting of necropsy cardiac specimens and illustrates some of the pathologic cardiac abnormalities cut in these tomographic planes. Part I of this report describes position of the heart and tomographic axis planes, preparation of the heart and methods of cutting at necropsy, and the short-axis, two-chamber, and four-chamber views of the heart.