This booklet focuses on classic autism, pervasive developmental disorder not otherwise specified (PDD-NOS), and Asperger syndrome, with brief descriptions of Rett syndrome and childhood disintegrative disorder. The booklet describes possible indicators of autism spectrum disorders (ASD), their diagnosis, available aids, treatment options, adults with ASD, research into causes and treatment of ASD, and the Children's Health Act of 2000, and what it means to autism research. The addendum to this booklet was prepared to clarify information contained in the booklet; and to provide updated information on the prevalence of autism spectrum disorders. Specifically, the addendum addresses prevalence, Fragile X, medications, and disorders/vaccinations.