The syndrome of complete androgen insensitivity is an X-linked inherited disorder resulting in marked inhibition of androgen action. The following case illustrates a subject with complete androgen insensitivity who, despite being a genetic and gonadal male, presents as a phenotypic female with primary amenorrhea, normal breast development, and lack of axillary and pubic hair. The diagnosis, pathophysiology, and management of the condition are discussed, as well as recently identified abnormalities in the androgen-receptor gene. The partial forms of androgen insensitivity are also included in the discussion.