According toDSM-IV-TR,gender identitydisorder (GID)(also known as transsexualism) has two features: a strong and persistent cross-gender identification and persistent discomfort about one’s assigned gender or a sense of inappropriateness in the role of that gender. It is reportedly a rare disorder, with prevalence rates between 1:12,000 and 1:40,000 in western countries (Landen, Walinder, & Lundstrom, 1996). Though the etiology is largely unknown, genetic factors have been reported to play an important role, based on reports of twin concordance and families with several affected members (Green, 2000). Althoughchromosomalabnormalitieshavenotbeen reported to occur at an increased rate in these patients, rare reports of chromosomal abnormalities in GID have been reported (Table 1). Klinefelter’s syndrome (KS) is the most common sex chromosome disorder and the second most common condition caused by the presence of extra chromosomes. The condition exists in roughly one out of every 1,000 males and is characterized by chromosomal abnormality in the form of 47,XXY karyotype with a male phenotype. Males with KS may have a mosaic 47,XXY/46,XY constitutional karyotype and varying degrees of spermatogenic failure. Mosaicism 47,XXY/46,XX with clinical features suggestive of Klinefelter syndrome is very rare. Thus far, only about 10 cases have been described in the literature (Velissariou et al., 2006). Few reports of sex reversal in KS have been reported. Mutations in theSRY orSOX genehavebeen implicated insex reversal (Cameron & Sinclair, 1997). As per our knowledge, so far there are only three reports of complete sex reversal in this syndrome searchable on PubMed (Rottger et al., 2000; SaavedraCastillo, Cortes-Gutierrez, Davila-Rodriguez, Reyes-Martinez, OThangaraj,Gupta,Chakravarty,& Singh, 1998). We present a rare case, probably the first of its kind, in which a XXY female presented to us with transsexualism. X, a 24-year-old, single, graduate, employed female patient was referred to our department for psychiatric evaluation in view of her request for sex reassignment surgery. She introduced herself to us as a male. On psychiatric interview, she reported that, since her childhood, she had experienced sexual interest in girls, preferred dressing like a boy, played mainly with boys, would take the role of boys in games, and had been predominantly interested in masculine activities, such as playing football. She would find it difficult to use female restrooms and would often be teased by people around her. She could not understand what and who she was and, at times, would even consider herself a hermaphrodite. It was revealed that she had feelingsofdiscomfortwithherown gender, and thedesire to be male since her childhood. Birth history revealed that she was a full term, normal vaginal delivery. Parents had no doubt regarding the anatomical sex of her and reared her like a female. There were no family conflicts or any difference in her rearing as compared to her other siblings. There was neither significant family history nor any history suggestive of mental subnormality or psychosis. Menstrual history revealed that her first and only menstruation occurred at the age of 15–16 years. This was very scanty. She was started on hormonal therapy, but did not resume menstruation. She has homosexual contact with a female and was not guilty of the same. The Gender Identity/Gender Dysphoria Questionnaire for Adolescents and Adults (Deogracias et al., 2007) was applied. It is a scale designed to assess gender identity (gender dysphoria) A. Khandelwal R. C. Jiloha Department of Psychiatry, Maulana Azad Medical College and Associated GB Pant Hospital, New Delhi, India