Previous work investigating frequency encoding mechanisms in human auditory cortex has provided evidence that latency of the auditory evoked M100 is strongly proportional to frequency, with low frequency (100^200 Hz) tones associated with B30 ms longer latencies than mid-range frequency (1^2 kHz) tones. Motivated by pervasive speech and auditory perception de¢cits observed in autism spectrum disorder, we evaluated M100 frequency dependence in children with autism disorder and typically developing controls.Results indicate that for control children, the dynamic range of frequency modulation was similar to previous reports for healthy adults. Children with autism had a much reduced range of modulation in right hemisphere sites. Findings indicate that frequency encoding mechanisms may follow a di¡erential maturational path in autism spectrum disorder.