The first chapter of Volume One contains a meta-analysis of studies comparing sleep in people with and without intellectual disabilities. The key finding was that people with intellectual disabilities slept for, on average, 23 minutes less each night and experienced poorer sleep quality. Chapter Two details an empirical study of sleep in children with Autism Spectrum Disorders (ASD) and a parent-identified sleep problem. Actigraphy and diary measures found no differences between the children with ASD and a typically developing comparison group. Questionnaires identified numerous sleep problems that were more commonly reported in the children with ASD. Chapter Three is a lay summary of the previous chapters