Autism spectrum disorders (ASD) are a heterogeneous group of neurodevelopmental disorders defined behaviorally by abnormalities in social, verbal, and nonverbal communication. The etiologies of ASD are unknown, likely to be the result of a variety of numerous genetic, neurological, environmental, and immunological interactions that lead to a general behavioral phenotype defined as ASD. This review will focus on the various immune system anomalies, in particular, autoantibodies, which have been reported in subjects with ASD. In addition, we will discuss recent studies performed by our group concerning the presence of autoantibodies directed against neural antigens, which are observed in patients with ASD.