Autism manifests itself in various and particularly detailed ways, especially as it interacts with differences in class, gender, race, and age. Misunderstandings and misinformation about diverse and different presentations mean that poorly diagnosed people and those who receive no diagnosis at all often fail by the medical, educational, social, and criminal justice systems. This comprehensive resource will help multidisciplinary professionals better understand, position, and identify the differentiated presentations of autism. It includes an overview of the autism diagnosis process, an exploration of controversial and often confusing diagnoses such as PDA, ODD, CD, ASPD, and BPD; discussions on best practices in FII research; and analysis of the specific challenges of diagnosing autism concerning women and girls, BAME communities, schools, and the criminal justice system.