Adrenergic receptors in the enteric nervous system (ENS) are important in control of the gastrointestinal tract. Here we describe the distribution of adrenergic receptors in the ENS of the ileum and colon of the guinea pig, rat, and mouse by using single- and double-labelling immunohistochemistry. In the myenteric plexus (MP) of the rat and mouse, α2a-adrenergic receptors (α2a-AR) were widely distributed on neurons and enteric glial cells. α2a-AR mainly colocalized with calretinin in the MP, whereas submucosal α2a-AR neurons colocalized with vasoactive intestinal polypeptide (VIP), neuropeptide Y, and calretinin in both species. In the guinea pig ileum, we observed widespread α2a-AR immunoreactivity on nerve fibers in the MP and on VIP neurons in the submucosal plexus (SMP). We observed extensive β1-adrenergic receptor (β1-AR) expression on neurons and nerve fibers in both the MP and the SMP of all species. Similarly, the β2-adrenergic receptor (β2-AR) was expressed on neurons and nerve fibers in the SMP of all species, as well as in the MP of the mouse. In the MP, β1- and β2-AR immunoreactivity was localized to several neuronal populations, including calretinin and nitrergic neurons. In the SMP of the guinea pig, β1- and β2-AR mainly colocalized with VIP, whereas, in the rat and mouse, β1- and β2-AR were distributed among the VIP and calretinin populations. Adrenergic receptors were widely localized on specific neuronal populations in all species studied. The role of glial α2a-AR is unknown. These results suggest that sympathetic innervation of the ENS is directed toward both enteric neurons and enteric glia. J. Comp. Neurol. 495:529–553, 2006. © 2006 Wiley-Liss, Inc.