An attention-independent negative wave-form termed 'mismatch negativity' (MMN) of the auditory event-related potentials (ERPs) was studied in ten children (3-6 years) with developmental dysphasia and in fourteen control children (3-7 years) with normal speech and language development. The MMNs were elicited with pure sine tone stimuli using the oddball paradigm. The peak latency and peak amplitude of MMN response to frequency (500/553 H2) difference was measured. The grand average amplitude of frequency MMN was significantly attenuated in dysphasic children as compared to controls, but no significant difference was observed in the latency of peak frequency MMN. The results indicate that dysphasic children have a defect in automatic auditory processing of frequency differences. Because the MMN response reflects central auditory processing and is modal specific for auditory stimuli we argue that the MMN method can serve as an objective tool to assess central auditory deficits in children.