The purpose of this chapter is to review the presentation and management of patients affected by conditions of abnormal sex differentiation. First, the processes of normal sex differentiation are covered, followed by an overview of the various syndromes of abnormal sex differentiation, or intersex conditions, that can occur. These disorders are presented according to the following categories: patients who possess a 46,XX chromosome complement, those who possess a 46,XY chromosome complement, and individuals who present with an atypical sex chromosome complement (i.e. 45,XO or 45,X0/46,XY mosaicism). A description of the medical, surgical and psychological treatment options for people affected by various intersex conditions and reared as females are included. Practice points, based on research studies when available, are dispersed throughout the chapter. Additionally, information pertaining to relevant Internet websites and patient support groups are provided, so that medical staff can educate their patients about the availability of these resources.