The characteristic feature of autistic spectrum disorder (ASD) is impairment in social interaction and communication. These features are also seen in schizoid personality disorder (Cluster A PD) where pateint prefer solitary activities and is emotionally cold and detached. There can be significant difficulty differentiating between schizoid PD and milder forms of ASD. It must be remembered that patients with ASD have more severe social impairment and also have stereotypical behaviours and interests.