Congenital adrenal hyperplasia (CAH) is a group of autosomal recessive disorders caused by enzymatic defects in the corticosteroid synthesis pathway leading to an increase in the serum level of ACTH and adrenocortical hyperplasia (
1). They are mainly resulted from mutations in the genes of the enzymes that mediate the biochemical steps of corticosteroids production from cholesterol by the adrenal glands such as 21-hydroxylase (
2). These conditions involve excessive or deficient production of sex steroids and thus sometimes alter developing sex characteristics in affected fetus (
3). One of the major clinical manifestations of this abnormality is disorder of sex development (DSD) that is characterized by initial difficulty in identifying the gender according to external genitalia (
4). A long-standing and fundamental question for psychologists, sociologists, biologists, and many other scientists is “how differences in sex behavior arise?” and thereby, many studies have been conducted in different species of animals (
5). Androgen plays a key role in the development of male sexual phenotype, behavior, sexual orientation, and gender identity (
6). In this regard, an increase in the male hormones not only can lead to the change of external genitalia, but also may alter sexual behavior. Gender identity refers to an individual’s subjective internal sense of being a male or a female. Usually, most children can label their gender identity by the age of 3 years. Gender identity remains stable over time, but it may change in a small number of persons (
7). Adults with gender identity disorder find occupation for living as a person of the opposite sex that may be manifested by intense desire for social role of the opposite sex or by obtaining the physical appearance of the opposite sex through hormonal or surgical manipulation (
8). In addition, these patients try to appear as a member of the opposite sex population (
9). Different ideas about the time of sex assignment of a child with DSD exist; some psychologists have the opinion to postpone it after puberty and then to act according to the desire of the patient. Some authors say that it should be done according to the grade of virilization and the girls with more severe virilization should be reared as a boy. On the other hand, when a baby is born, the first question is about the gender, and mother imagines the life of her child according to the gender that may not be specified by the examination of external genitalia in patients with DSD. All the relatives in Iran ask about the gender of the newborn. Thus, DSD is a medical emergency for assignment of appropriate rearing gender of the neonate. It is difficult to change the gender of a child with CAH when is reared with the opposite sex not only due to social and personal aspects, but also because of the correcting genital surgery that had been done during infancy. This study has been done to clarify which factors affect gender identity in patients with CAH, and what and when should be a gender assigned to a child with CAH and DSD.