Melanin-concentrating hormone (MCH) is a cyclic neuropeptide that has been initially characterized from a salmon pituitary extract and subsequently identified in various species from all classes of vertebrates. The present review summarizes the current knowledge regarding the neuroanatomical distribution of MCH-immunoreactive neurons in submammalian vertebrates. In all species examined, MCH-immunoreactive perikarya are confined to the hypothalamus, with the exception of the cyclostome Lampetra fluvialis and the lungfish Protopterus annectens, in which additional populations of MCH-immunoreactive cell bodies occur in the telencephalon, and the frogs Rana ridibunda and Rana esculenta which exhibit MCH-positive perikarya in thalamic nuclei. In teleosts, in the frog R. ridibunda and in the L. fluvialis, MCH is present in the classical hypothalamic-neurohypophysial system indicating that the peptide may play the role of a neurohormone. In other groups, MCH-immunoreactive nerve fibers are widely distributed in various brain regions suggesting that, in these species, MCH in the central nervous system may act as a neurotransmitter or/and a neuromodulator rather than a neurohormone.