In recognition of the extensive use of the cat as an experimental model of cardiac innervation, the effects of electrical stimulation of stellate ganglia, thoracic vagosympathetic complexes, and individual feline cardiopulmonary nerves on heart rate, blood pressure, and contractility in all four cardiac chambers were analysed and correlated with the anatomy of the thoracic autonomic nervous system. The right and left stellate ganglia in cats are relatively large and globular. Distinct dorsal and ventral ansae subclavia arise from these ganglia, connecting with the relatively small, spindle-shaped middle cervical ganglia situated in the apices of the thoracic cage bilaterally. A cranial pole nerve arises from each of the middle cervical ganglia and courses cranially to unite with the ipsilateral superior cervical ganglia. On each side, the major cardiopulmonary nerves arise from the middle cervical ganglion, the relatively large vagosympathetic trunk, and the stellate ganglion. On the right side these nerves consist of a very small right stellate cardiac nerve, a recurrent cardiac nerve, a group of craniovagal nerves and a group of caudovagal cardiopulmonary nerves. On the left side are the left stellate cardiac, ventrolateral, ventromedial, and innominate cardiopulmonary nerves. All of these nerves contain efferent parasympathetic and/or sympathetic fibers which modify cardiac chronotropism and/or inotropism. Some contain afferent fibers. These results indicate that specific cardiopulmonary nerves exist in cats, which when stimulated, modify the cardiovascular system in specific fashions.