Autism spectrum disorder is a complex condition that requires specialised care. Knowledge of the costs of autism spectrum disorder, especially in comparison with other conditions, may be useful to galvanise policymakers and leverage investment in education and intervention to mitigate aspects of autism spectrum disorder that negatively impact individuals with the disorder and their families. This article describes the services and associated costs for four groups of individuals: adolescents with autistic disorder, adolescents with other autism spectrum disorders, adolescents with other special educational needs and typically developing adolescents using data from a large, well-characterised cohort assessed as part of the UK Special Needs and Autism Project at the age of 12 years. Average total costs per participant over 6 months were highest in the autistic disorder group (11,029), followed by the special educational needs group (9268), the broader autism spectrum disorder group (8968) and the typically developing group (2954). Specialised day or residential schooling accounted for the vast majority of costs. In regression analysis, lower age and lower adaptive functioning were associated with higher costs in the groups with an autism spectrum disorder. Sex, ethnicity, number of International Classification of Diseases (10th revision) symptoms, autism spectrum disorder symptom scores and levels of mental health difficulties were not associated with cost.