Forty of 54 children with autism were reported to have an elevated antibody response to GM1 ganglioside that correlated with disease severity.1 Antiganglioside autoantibodies, especially those directed at GM1, are known to be associated with and play a pathogenic role in some immune-mediated peripheral neuropathies.2,3 The presumed link between autism and anti-GM1 antibodies, therefore, implies that testing may identify a sizable subset of patients who would benefit from immunomodulatory therapy. To evaluate the proposed association between autism and anti-GM1 antibodies, serum samples from children diagnosed with autism by strict clinical criteria and those without autism were analyzed using a standard, validated immunoassay protocol.