Gender identity disorder in girls is reported far less frequently than in boys. The analysis of a six-year-old adopted girl with gender identity disorder is presented to show the importance of the mother-infant relationship and of parental, especially maternal, attitudes toward gender in the normal development of gender identity and gender role definition. This child's unusual history included a late adoption, with clear evidence of separation trauma, and the ongoing influence of maternal infertility. Her symptoms of gender identity disorder appeared before her second birthday and were well established by three years of age. The analysis, from age six to thirteen, achieved a better adaptation to her gender. Her masculine strivings gradually became incorporated into an essentially feminine orientation.