BACKGROUND We assessed motion processing in a group of high functioning children with autism and a group of typically developing children, using a coherent motion detection task. METHODS Twenty-five children with autism (mean age 11 years, 8 months) and 22 typically developing children matched for non-verbal mental ability and chronological age were required to detect the direction of moving dots in a random dot kinematogram. RESULTS The group of children with autism showed significantly higher motion coherence thresholds than the typically developing children (i.e., they showed an impaired ability to detect coherent motion). CONCLUSIONS This finding suggests that some individuals with autism may show impairments in low-level visual processing--specifically in the magnocellular visual pathway. The findings are discussed in terms of implications for higher-level cognitive theories of autism, and the suggestion is made that more work needs to be carried out to further investigate low-level visual processing in autism.