Results indicate that there were considerable differences in criminal behavior between subgroups of people with PDD; overall, serious crime is a rare occurrence in people with PDD. Criminal behavior was very uncommon in the child autism group compared to the comparison. The low prevalence of crime in the childhood autism group may be due to the more protected environments of these individuals and close monitoring in institutions for mentally retarded autistic people. As expected, females were found to have a much lower rate of conviction than males in the comparison sample. As far as types of criminal behavior are concerned, the findings suggest that people belonging to case groups tended to commit more serious crimes than people from the comparison groups; however, only arson statistically separates Asperger’s Syndrome (AS) cases from the comparison group, whereas sexual offending approaches statistical significance. In several case reports, particular attention has been given to violence, sexual offenses, and arson in AS. The study sample included 313 children with variants of PDD consecutively seen as in-patients at the University Clinics of Child Psychiatry at Copenhagen and Aarhus during the 25-year period 1960 to 1984. Together, the two clinics provided services to all of Denmark. At the time most children with supposed autism or other extensive developmental disorders were admitted as in-patience. A control group was drawn from the Danish central persons register (n=933) from the general population. Tables, references