The auditory event-related potential waveform termed "mismatch negativity" was examined in 12 mentally retarded children with delayed development of speech and language (aged 5-8 years) and in 13 children with developmental dysphasia (aged 5-9 years). The mismatch negativity waves were elicited with pure sine-wave tone stimuli using the oddball paradigm. We measured the peak latency and peak amplitude of mismatch negativity responses to frequency (500/553 Hz) difference. The mismatch negativity patterns were compared with those of 10 children with normal development of linguistic skills (aged 5-9 years). In both the mentally retarded and dysphasic groups, the peak amplitude of the frequency mismatch negativity was significantly attenuated when compared with the control group, but no significant difference was observed between the mentally retarded and dysphasic groups. Attenuated frequency mismatch negativity was related to impairment of linguistic skills irrespective of the child's cognitive skills. Because the mismatch negativity response reflects central auditory processing and is modal specific for auditory stimuli, this change-specific response can serve as an objective tool to elucidate central auditory deficits in children.