The Intersex Society of North America closed its doors and stopped updating this website in 2008. ISNA’s work is continued by interACT: Advocates for Intersex Youth , who proudly preserves this website as a historical archive. For current information, links to intersex support groups, and to connect with intersex advocates, please head to interACT: Advocates for Intersex Youth .

# How common is intersex?

To answer this question in an uncontroversial way, you’d have to first get everyone to agree on what counts as intersex —and also to agree on what should count as strictly male or strictly female. That’s hard to do. How small does a penis have to be before it counts as intersex? Do you count “sex chromosome” anomalies as intersex if there’s no apparent external sexual ambiguity?[1] (Alice Dreger explores this question in greater depth in her book Hermaphrodites and the Medical Invention of Sex.)

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. The basis for that article was an extensive review of the medical literature from 1955 to 1998 aimed at producing numeric estimates for the frequency of sex variations. Note that the frequency of some of these conditions, such as congenital adrenal hyperplasia, differs for different populations. These statistics are approximations.

Not XX and not XY one in 1,666 births

Klinefelter (XXY) one in 1,000 births

Androgen insensitivity syndrome one in 13,000 births

Partial androgen insensitivity syndrome one in 130,000 births

Classical congenital adrenal hyperplasia one in 13,000 births

Late onset adrenal hyperplasia one in 66 individuals

Vaginal agenesis one in 6,000 births

Ovotestes one in 83,000 births

Idiopathic (no discernable medical cause) one in 110,000 births

Iatrogenic (caused by medical treatment, for instance progestin administered to pregnant mother) no estimate

5 alpha reductase deficiency no estimate

Mixed gonadal dysgenesis no estimate

Complete gonadal dysgenesis one in 150,000 births

Hypospadias (urethral opening in perineum or along penile shaft) one in 2,000 births

Hypospadias (urethral opening between corona and tip of glans penis) one in 770 births

Total number of people whose bodies differ from standard male or female one in 100 births

Total number of people receiving surgery to “normalize” genital appearance one or two in 1,000 births

We were recently asked to update these frequency figures, and a lively discussion arose between two staff members.