Ten-month-old infants and adults were tested in an auditory oddball paradigm in which 50-ms tones were separated by 1500 ms (standard interval) and occasionally 500 ms (deviant interval). Both infants and adults showed marked brain responses to the tone that followed a deviant inter-stimulus interval (ISI). Specifically, the timing-deviance event-related-potential (ERP) difference waves (deviant-ISI ERP minus standard-ISI ERP) yielded a significant, fronto-centrally distributed, mismatch negativity (MMN) in the latency range of 120-240 ms post-stimulus for infants and 110-210 ms for adults. A robust, longer latency, deviance-related positivity was also obtained for infants (330-520 ms), with a much smaller and later deviance-related positivity observed for adults (585-705 ms). These results suggest that the 10-month-old infant brain has already developed some of the same mechanisms as adults for detecting deviations in the timing of stimulus events.