NeuroNames is an integrated nomenclature for structures in the brain and spinal cord of the four species most studied by neuroscientists: human, macaque, rat and mouse. It offers a standard, controlled vocabulary of common names for structures, which is suitable for unambiguous neuroanatomical indexing of information in digital databases. Terms in the standard vocabulary have been selected for ease of pronunciation, mnemonic value, and frequency of use in recent neuroscientific publications. Structures and their relations to each other are defined in terms of the standard vocabulary. Currently NeuroNames contains standard names, synonyms and definitions of some 2,500 neuroanatomical entities.