The United States affiliate of the Organization Intersex International (OII)

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What is Intersex?


INTERSEX refers to congenital biological sex which is not typically male or female. Intersex people refers to people born with, or who develop naturally in puberty, biological sex characteristics known as Intersex Traits which are not typically male or female.

Intersex traits comprise chromosomes, genitals, hormones and/or gonads that do not fit typical definitions of male or female, and can result in additional variations in secondary sexual characteristics such as muscle mass, hair distribution, breast development, hip to waist ratio and stature.

Intersex is not a single category – many forms of intersex exist. Within each form, there may be substantial variation as well, including individuals with highly typical male and female appearances.

An intersex person may have any sexual orientation: heterosexual, homosexual, bisexual, queer, etceteras. Intersex is historically defined by biology, rather than gender identity, as intersex people experience the same range of gender identities as non-intersex people do. We note, however, that the terms “male” and “female”– once labels traditionally defined by biology– no longer are, as trans* people demonstrate. We also note that some intersex people have discussed that “intersex” describes their gender identity as well as the sex characteristics they were born with. Thus an exclusively biologically determinist view of “intersex” may not be viable, culturally speaking, nor would an increase in our population (due to, some claim, transgender use of the label “intersex”), necessarily be harmful to our efforts in attaining equal human rights.


The most thorough existing research finds intersex people to constitute an estimated 1.7% of the population*, which makes being intersex about as common as having red hair (1%-2%). However, popularly misinterpretted, much referenced statistics would have you believe are numbers are much lower. Here’s why.

Some groups use an old prevalence statistic that says we make up 1 in 2000, or .05%, percent of the population, but that statistic refers to one specific intersex trait, ambiguous genitalia, which is but one of many variations which, combined (as they are in medical diagnostics and coding), constitute the 1.7% estimate by esteemed Professor of Biology and Gender Studies, Anne Fausto-Sterling, of Brown University*.

A similar, slightly higher, statistic was also reported in, “How Sexually Dimorphic Are We?”, by Blackless, et al, in The American Journal of Human Biology. “The belief that Homo sapiens is absolutely dimorphic with the respect to sex chromosome composition, gonadal structure, hormone levels, and the structure of the internal genital duct systems and external genitalia, derives from the platonic ideal that for each sex there is a single, universally correct developmental pathway and outcome. We surveyed the medical literature from 1955 to the present for studies of the frequency of deviation from the ideal male or female. We conclude that this frequency may be as high as 2% of live births. The frequency of individuals receiving “corrective” genital surgery, however, probably runs between 1 and 2 per 1,000 live births (0.1–0.2%).” Am. J. Hum. Biol. 12:151–166, 2000. © 2000 Wiley-Liss, Inc.;2-F/abstract These two findings are the most thorough scientific research which exists on the statistical prevalence of congenital intersex traits in humans.

The erroneous belief that we are an extremely tiny percentage of the population is often used to dismiss our need for legal rights and protections. We therefore encourage everyone — particularly allies and/or members of the press educating others about intersex people — to please use the information and prevalence statistic provided here to accurately do so. Thank you!

 * Fausto-Sterling, Anne (2000). Sexing the Body: Gender Politics and the Construction of Sexuality. New York: Basic Books. ISBN 0-465-07713-7.

* The Intersex Society of North America (ISNA, 1993-2008), popularized the “1 in 2000” (.05%) statistic, but clarified on its website:
“Here’s what we do know: If you ask experts at medical centers how often a child is born so noticeably atypical in terms of genitalia that a specialist in sex differentiation is called in, the number comes out to about 1 in 1500 to 1 in 2000 births. But a lot more people than that are born with subtler forms of sex anatomy variations, some of which won’t show up until later in life. Below we provide a summary of statistics drawn from an article by Brown University researcher Anne Fausto-Sterling….”

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