Autism spectrum disorder (ASD) is a neurodevelopmental disorder of behavior that presents in childhood. It is a clinically heterogeneous disorder of behavior, characterized by two features - (1) impairment in social communication and interaction and (2) repetitive patterns of behavior. The diagnosis is essentially clinical and is based primarily on history-taking and observation of the child over a period. There are several standardized screening tools and scales available to help make a diagnosis. Children with autism often present with speech delay and this has to be distinguished from other conditions. ASD is often associated with comorbid conditions which have to be identified to tailor the treatment program for each child. It is important that the parents or caretakers of the child are involved in the process of assessment and diagnosis and that their misconceptions and fears are addressed.