Background: To compare childhood arrestees with matched comparison groups on levels of autistic symptoms and to assess the unique predictive value of autistic symptoms for future delinquent behavior in childhood arrestees. Methods: Childhood first-time arrestees (n = 308, baseline age 10.7 ± 1.5 years) were followed up for 2 years. Autistic symptoms, externalizing disorders and delinquent behavior were assessed yearly. Childhood arrestees were compared on autistic symptoms with matched (age, gender) general population and clinical autism spectrum disorder samples. The predictive value of autistic symptoms for delinquent behavior was analyzed using generalized estimating equations. Results: At each assessment, levels of autistic symptoms in childhood arrestees were in between levels found in the general population and autism spectrum disorder samples. Autistic symptoms were positively associated with delinquent behavior in childhood arrestees, even after adjustment for externalizing disorders: IRR (incidence rate ratio) 1.23; 95% CI 1.11-1.36 and IRR 1.29; 95% CI 1.15-1.45 for core autistic symptoms and total symptom score, respectively. Conclusions: Autistic symptoms are more prevalent in childhood arrestees compared to the general population and are uniquely associated with future delinquent behavior. Attention should, therefore, be given to the possible presence of autism related symptomatology in these children. Implications for diagnostic assessment and intervention need further investigation. © 2011 Association for Child and Adolescent Mental Health.