Money and Brennan (1968) reported on the gender identity of six female patients whom they labeled as transsexuals. Indeed, five had undergone a mastectomy and hysterectomy. Three patients had also begun surgery for the construction of an artificial penis. The patients were older than their male counterparts (i.e. male transsexuals in their program) with the average age being 37.5 years (range 32 51), and were of bright normal intelligence (IQ range 97 131).

Benjamin suggested that the etiology of female transsexualism involved early childhood conditioning, and constitutional predispositional factors. He seemed to believe that one day researchers would uncover an innate biological factor underlying transsexualism.

With the publication of Benjamin's The Transsexual Phenomenon (1966) a new era of research into the spectrum of gender identity disturbances began. This was the first major clinical book to go beyond the single case study and present data on a large number of individuals (n = 172) who had requested evaluation for sex reassignment surgery (whom he labeled "transsexuals").

McCully (1963) reported on the projective test findings of a 32 year old Catholic woman who wished to change her sex. The patient, the youngest of two female siblings, had an early identification with males (age 5) and was a tomboy during latency. She described her father as "a volatile person who was sometimes physically abusive" to her.

By 1953 it was clear that female transsexualism was not isolated to a few rare cases. After the celebrated Christine Jorgenson case, Hamburger (1953) reported that 108 women sent him letters from all over the world requesting SRS. The age distribution ranged from 15-55, with the ratio of females requesting information being 1:4. Only one of the women reported being married and six were divorced.

In 1949 Cauldwell reported on the case of a woman who desired to become a man. He labeled the disorder "psychopathia transsexualis" and thereby introduced the term "transsexual" into the clinical literature. With some degree of chagrin, Pauly (1974a) noted that it took almost twenty seven years from the time of Hirschfeld's initial report of female transsexualism until Cauldwell's presentation in 1949.