A coronary chemoreceptor and its neighboring nerves and ganglia were studied by serial section from the hearts of 11 victims of sudden unexpected death. Either focal or extensive inflammatory destruction was present in the chemoreceptors of 10 of the 11 hearts, and similar abnormalities of local nerves and ganglia were present in all 11 hearts. Because an identical coronary chemoreceptor in the dog has previously been shown to be the site of origin of a powerful reflex with major influence on the electrical activity of the heart, the functional significance of the neural abnormalities found in these 11 human hearts may include important distortion of cardiac rhythm, conduction or repolarization. Future studies are needed to determine the prevalence of such lesions in the hearts of other victims of sudden death and among control subjects, as well as to determine the etiology of this special neuropathology of the heart.