INTRODUCTION: The coronary arterial system has been the subject of greater investigation than its venous system due to the importance of human coronary artery disease. With the advent of new percutaneous treatments, the anatomy of the coronary venous system has increasing relevancy. We compared the organization of the coronary venous circulation in three species commonly used in research and compared these to normal humans using both macroscopic anatomic and angiographic studies. ANIMALS: The anatomy of five explanted hearts from healthy dogs, pigs, and sheep were studied macroscopically, and 10 explanted hearts per animal species and 10 clinically normal human were examined by angiography. METHODS: Animal hearts were injected with latex and dissected macroscopically. The coronary venous system of humans was evaluated from clinical angiographic studies. In the animal hearts, a retrograde angiographic study was performed via a Foley catheter in the coronary sinus. RESULTS: The general organization of the coronary venous circulation was similar among humans, dogs, sheep, and pigs. Despite overall similarities to humans, animal hearts demonstrated the absence of the oblique vein of the left atrium and differences in position and organization of venous valves; venous diameters; number of tributary veins; and presence of an anastomosis between the left and right (human anterior and posterior) venous tree. The left azygos of the pig and sheep joined the coronary sinus. CONCLUSIONS: Anatomical differences must be considered when planning biomedical and veterinary studies incorporating cardiac veins. This study provides baseline data regarding structure and organization of the cardiac venous system.