We report here event-related potentials (ERPs) of human newborns to occasional pitch changes in a repetitive sequence of tone pips. These pitch changes elicited a large slow negative ERP component which resembles the mismatch negativity (MMN) generated by the adult brain under similar conditions. This MMN-type of negativity in newborns suggests that already at this early ontogenetic stage the brain monitors the acoustic environment for a possible change in any of its repetitive aspects. Apart from its theoretical interest, this finding might provide a new way to test the development of the central nervous system and to diagnose cerebral dysfunction at a very early stage.