The morphology of the superficial cardiac veins draining the coronary sinus was investigated in 47 normal adult dogs, using the injection-corrosion-fluorescence technique. The veins pertaining to the left coronary territory all drain directly to the coronary sinus and include the following vessels: the great coronary vein and its tributaries, the left posterior atrial and ventricular veins. The veins pertaining to the right coronary territory include the posterior interventricular vein and the small cardiac vein. A comparison with the human pattern was made, particularly regarding the number of interventricular septal branches and it was suggested that such a reduction in number in the dog could be due to a take-over from the Thebesian veins in the venous drainage of the interventricular septum.