Autism spectrum disorder (ASD) refers to a type of developmental disability caused by brain differences. ASD patients frequently struggle with social engagement and communication, as well as confined or repetitive activities or interests. Additionally, people with ASD have a distinct manner in which they learn, move or pay attention. Young adults and adolescents with ASD may struggle to develop and keep friendships, communicate with adults and peers, or comprehend the appropriate behaviors expected in the workplace or at school. There are several risk factors associated with ASD, including genetic, environmental and biological factors. There are no medical tests to diagnose ASD and the individual's development stage and behavior is assessed for diagnosis. ASD treatments aim to alleviate symptoms that affect quality of life and daily functioning. Treatment plans are typically collaborative and tailored according to the individual requirements. This book discusses the evaluation and assessment of autism spectrum disorder. A number of latest researches have been included herein to keep the readers up-to-date with the global concepts in this medical condition.