Benjamin scale
The Sex Orientation Scale was Harry Benjamin's attempt to classify and understand various forms and subtypes of transvestism and transsexualism in biological males, published in 1966. It was a seven-point scale ; it was analogous to the Kinsey Scale as it relates to sexual orientation, which also had seven categories. Much like Kinsey's understanding of sexual orientation, Benjamin understood the nature of gender identity and gender expression not as a discrete scale, but as a spectrum, a continuum with many variations. However the Benjamin scale does not reflect a modern understanding of gender identity and is not useful as a contemporary diagnostic tool, especially due to its conflation of gender identity with sexual orientation.
Sex Orientation Scale (S.O.S.)
Sex and Gender Role Disorientation and Indecision| Group | Type | Name | Kinsey scale | Conversion operation? |
| 1 | I | Transvestite | 0-6 | Not considered in reality |
| 1 | II | Transvestite | 0-2 | Rejected |
| 1 | III | Transvestite | 0-2 | Actually rejected, but idea can be attractive |
| 2 | IV | Transsexual | 1-4 | Attractive but not requested or attraction not admitted |
| 3 | V | Transsexual | 4-6 | Requested, usually indicated |
| 3 | VI | Transsexual | 6 | Urgently requested and usually attained; indicated |
Benjamin noted, "It must be emphasized again that the remaining six types are not and never can be sharply separated."
Benjamin added a caveat: "It has been the intention here to point out the possibility of several conceptions and classifications of the transvestitic and the transsexual phenomenon. Future studies and observations may decide which one is likely to come closest to the truth and in this way a possible understanding of the etiology may be gained."
Benjamin's Scale references and uses Alfred Kinsey's sexual orientation scale to distinguish between "true transsexualism" and "transvestism".