Within psychology and psychiatry, gender identity has developed at least two distinguishable meanings: awareness of anatomy and endorsing specific traits that are stereotypical of different gender groups. However, neither existing approach has considered gender identity to be a self-categorization process that exists within personality science. In this book, gender identity is examined as a disorder, along with developmental perspectives and social implications. Some of the topics discussed include gender identity as a personality process; the intersection of gender and sexual identity development in a sample of transgender individuals; gender dysphoria; representations of teachers about the relation between physical education contents and gender identities; and common hypothetical etiology of excess androgen exposure in female-to-male transsexualism and polycystic ovary syndrome.