What makes this case particularly interesting is that D was found to have an unusual chromosomal disorder, 48,XXYY syndrome. Very little is known about this condition, since only 60 or so cases have been reported in the literature; there is no known association of this syndrome with sexually abusive behavior. Following a presentation of D's case history, the assessment and treatment of his sexually abusive behavior is described, most of which occurred while he was detained in secure accommodation after his first known offense (indecent assault) at the age of 12. The cognitive-behavioral treatment program apparently had little effect in reducing his risk of reoffending. He lacked interest in and motivation for change, so it proved difficult to engage him in interventions aimed at changing his attitudes and behavior. Further, he was apparently unable to understand the emotional consequences for the victims of his abusive behavior. Consequently, he continues to be sexually aroused by children, experiencing sadistic sexual fantasies, and to hold beliefs that support sexual involvement with children. Despite the risk of sexual reoffending, D was recently released from security shortly before his 18th birthday, moving into a community psychiatric setting with limited supervision. Two forensic psychiatrists concluded that he did not fully satisfy statutory criteria for detention under the English Mental Health Act of 1983, although both were of the opinion that he would pose a considerable threat to children if left unsupervised. Although the case of D is not typical of adolescent offenders held in secure accommodation, he is among the small number of dangerous juveniles released each year who cannot be detained beyond the age of 18 under current childcare legislation. 35 references