The carotid body (CB) is a neural crest-derived organ organized in clusters of neuron-like glomus cells surrounded by processes of glia-like sustentacular cells, which were classically believed to have a structural role. The organ is highly vascularized and densely innervated by afferent sensory fibers. The CB is a principal component of the homeostatic acute oxygen sensing system, required to activate the brain stem respiratory center to evoke hyperventilation during hypoxemia (Weir et al. 2005). The carotid body has also a remarkable structural plasticity since, unlike other neural tissues, it grows several folds its normal size upon maintained exposure to low blood oxygen tension (as it occurs during acclimation to high altitude or in patients with cardiopulmonary diseases presenting reduced lung gas exchange) (Edwards et al. 1971; Arias-Stella & Valcarcel, 1976). The processes underlying this classic response to hypoxia are essentially unknown. In the course of a systematic study of the pattern of cell proliferation in the CB of animals exposed to sustained hypoxia we have discovered a population of neural crest-derived progenitors in the adult CB. Although CB glomus cells can undergo mitosis, the growth of the organ mainly depends on the proliferation and differentiation of the stem cells, which form multipotent and self-renewing colonies in vitro (Pardal et al. 2007). The newly generated glomus cells have a normal phenotype (López-Barneo et al. 2001), they express voltage-dependent ion channels and respond to acute hypoxia and/or hypoglycemia with a surge of catecholamine release. Cell fate mapping experiments in vivo indicate that, unexpectedly, CB stem cells are a subpopulation of sustentacular cells. In vitro, these cells can be identified by their positive immunoreactivity to glial markers. In this respect, the neural crest derived CB progenitors resemble the stem cells identified in the neurogenic centers of the central nervous system (Doetsch, 2003). These observations identify the mammalian carotid body as a niche of neurogenesis with a recognizable physiological function in adult life. Besides its pathophysiological significance, CB stem cells could have potential clinical applicability.