Publisher Summary Arterial baroreceptors with medullated afferents have been studied extensively in many species, for example, dogs, rabbits, and rats. However, the arterial baroreceptor nerves also contain a large population of nonmedullated afferent fibers (C-fibers). Even the majority of the afferent fibers seem to be C-fibers. Thus, the aortic nerve of the cat contains about 10% medullated and 90% nonmedullated fibers. In a similar way, most of the afferent fibers from the heart are C-fibers. The characteristics of aortic baroreceptor C-fibers have been studied in more detail in rabbits, rats, and dogs. The characteristics of the aortic C-fibers in these three species are similar with rather high threshold and low discharge rates. Attempts have also been made to study reflexes from baroreceptor C-fibers. Thus, the electrical stimulation of the nonmedullated afferents in the aortic nerve evokes powerful depressor reflexes with a different pattern in comparison with reflexes evoked during the stimulation of medullated fibers.