The chapter provides an introduction to neurodevelopmental disorders and summarises recent advances in published research, focusing on the very early development and function of the human brain. The main influences on the current delivery and development of forensic healthcare services is set within the context of available policy and guidance, which is limited in part by the available research evidence to inform it. The book is divided into three sections. The first provides an overview with an introduction to individual disorders and covers aetiology, prevalence, comorbid mental disorder and relevant policy to date. The second section focuses on the clinical aspects of the range of disorders including screening, assessment, diagnosis, risk assessments and therapeutic approaches. The final section examines the pathways through the criminal justice system from police to court to disposal and addresses the specific aspect of fitness to plead or stand trial for those with neurodevelopmental disorders. This section also describes current relevant legislation within the UK as well as forensic services for those with such disorders from a national and international perspective.