People with autism spectrum disorder (ASD) display deficits/unusual behaviour in one of the three domains: Reciprocal social interaction, communication and restricted/repetitive interests/behaviours. The cause of ASD is still unknown, with etiological theories continuing to change as research progresses. It was once proposed that child-rearing was a major determinant, but more recent studies have suggested that the cause is multi-factorial, with genetics playing a substantial part in aetiology. Since awareness seems to be a precursor of increased prevalence, it would be interesting to note the awareness amongst young adults, who are the future parents of society. The awareness of these individuals may allow for the extrapolation of predicting whether the future prevalence of ASD will increase or decrease. In this book, the authors describe the awareness of young adults from Canada, United States, United Kingdom and Asia with respect to ASD.