This essential guide is a research-based practical handbook for assessing global developmental delay and other neurodevelopmental disorders in young children. It explains diagnostic, support, and treatment services available for children and their families, clarifying psychological and medical terminology, and global legislative and societal factors relating to assessment. Designed as a comprehensive compendium for student and practicing psychologists, it offers an introduction to historical perspectives around child development and developmental disorders, and how these have affected our understanding of neurodevelopmental disorders. It explains professional and ethical considerations surrounding the clinical practice of developmental assessments, and focuses on the crucial importance of understanding and supporting the parental experience of assessment and diagnosis. Key topics covered include: definitions and descriptions of genetic and chromosomal disorders and neurodevelopmental disorders; eligibility criteria for support and assistance; the Griffiths Scales, Bayley Scales, and other notable assessments for young children; autism spectrum disorder; the process of assessment and diagnosis, diagnostic tools, and report writing. Including a chapter of illustrative case studies of children with developmental disorders, this book will be essential reading for educational, clinical, and developmental psychologists working with children and their families, as well as post-graduate students training in the field.