Folie a deux is the transference of delusional ideas and behaviors from one person to another with whom there has been a close association. Its occurence in children has been rarely described in the literature, which was reviewed for case reports, diagnostic criteria, and etiological theories. A detailed case history of a 10-year-old girl who had delusions of special powers and delusions of persecution as well as hypochondriacal and hysterical symptoms is presented as an example of folie a deux between child and parent. This girl had developed a symbiotic incestuous relationship with her stepfather, a paranoid schizophrenic patient. Six criteria for making the diagnosis of folie a deux in a child were applied to the case studied. General and specific aspects of treating this disorder were discussed.