The pervasive developmental disorders (PDD's) are a group of neuropsychiatric syndromes with onset early in life characterized by deficits in language, socialization skills, and restricted behavior patterns. These include diagnostic categories that differ greatly, with respect to clinical presentation and long-term outcome, such as autistic disorder, Asperger’s disorder, Rett’s disorder, childhood disintegrative disorder, and PDD not otherwise specified. PDD's have been discussed as risk factors for criminal behavior, yet this association is untrue for the majority of patients. Individuals with PDD's may be at risk for legal trouble in the presence of comorbid psychopathology. The case studies of three adult patients with a PDD whose admission to hospital was precipitated by criminal behavior were analyzed. The presence of a disinhibiting affective illness, or driven motor activity, along with the inability to interpret social and emotional cues, was felt to contribute significantly to the patients’ legal troubles. The patients all demonstrated difficulties in appreciating social cues, had different degrees of interpersonal inappropriateness, and showed mannerisms and oddities. All three had abnormal neurologic findings and the presence of a major psychiatric illness in the context of a longstanding pervasive developmental problem. All met the diagnostic criteria for Asperger’s disorder. It was hypothesized that the delinquent behaviors described in these case studies resulted from comorbid psychopathology and not as a direct consequence of a developmental disorder. It is concluded that associations between neurodevelopmental syndromes and complex psychosocial behaviors are difficult to substantiate. Although there is a need to clarify this relationship, current limited evidence may trigger an unintended cycle that renders a neglected patient population vulnerable to further misunderstanding. 38 references