Autism spectrum disorder (ASD) refers to a set of neurodevelopmental disorders, comprising of autism, Asperger syndrome, childhood disintegrative disorder and pervasive developmental disorder not otherwise specified. Individuals with ASD experience problems with social interaction and communication, and exhibit restricted and repetitive patterns of behavior, activities and interests. Certain factors are associated with a high risk for ASD, such as having a family history of autism, certain genetic conditions, and having an older parent. A diagnosis of ASD can be established by the age of two. In autistic individuals, comorbidity is seen to increase with age. Autism Diagnostic Observation Schedule and Autism Diagnostic Interview-Revised are considered the fundamental standards of diagnosis. There is no cure for autism, but behavior therapy and special education programs early in life can impart the necessary skills. Different approaches, evaluations, methodologies and advanced studies on autism spectrum disorder have been included herein. Some of the diverse topics covered in this book address the varied conditions that fall under this category. This book is a vital tool for all researching and studying autism spectrum disorder.