This essay reviews current theories of gender identity disorders, with particular reference to the etiology of the problem in girls. The analysis of a latency-age girl with a serious cross-gender identity disorder is presented in detail. The case material illustrates the complex relationships among this girl's fantasies about her adoption, her ambivalent attachments to her adoptive parents and brother, her pet rats, and about herself as a boy. In the analytic work, the real and transferential connections to the analysts were explored, which enabled the patient to reenact the traumatic derailments in her early attachments, to begin to mourn her losses, and to move to a more feminine identification.