Afferent stimulation of one thoracic cardiopulmonary nerve generated compound action potentials in the efferent axons of other ipsilateral cardiopulmonary nerves in dogs, 14 days after their thoracic autonomic ganglia had been decentralized. The compound action potentials were influenced by the frequency of activation and (in 5 of 12 dogs) by pharmacological autonomic blocking agents (hexamethonium, atropine, phentolamine, and propranolol). Moreover, they were abolished transiently when chymotrypsin was injected locally into the ganglia, and extendedly when manganese was injected. Thus, synapses that can be activated by stimulation of afferent nerves exist in chronically decentralized thoracic autonomic nerves and ganglia. It is proposed that regulation of the heart and lungs occurs in part via thoracic autonomic neural elements independent of the central nervous system.