Inadequate length can limit the use of the internal mammary artery (IMA) for coronary revascularization. By following the shortest route from its origin to the recipient coronary artery. IMA use can be maximized. Seven cadavers were studied to determine that shortest route for the left and right IMAs. The shortest route for the left IMA to the left anterior descending coronary, diagonal, and circumflex coronary arteries was through the pericardium (p ≤ 0.01). For the right IMA, the significantly shortest routes were across the anterior heart for the left anterior descending and diagonal arteries, through the right pericardium for the right coronary artery or posterior descending artery, and through the pericardium and transverse sinus for the circumflex artery. Thus, any coronary artery can be reached with an in situ IMA, and the route through the pericardium is markedly shorter to ipsilateral coronary arteries.