The answer depends on exactly what you mean. The condition historically called “true hermaphroditism,” where a person is born with both ovarian and testicular tissue, is extremely rare: fewer than 1 in 20,000 births, with only about 500 cases documented worldwide. But the broader category of intersex conditions, where a person’s chromosomes, hormones, or anatomy don’t fit neatly into male or female, is significantly more common.
Why the Term Has Changed
The word “hermaphrodite” is no longer used in medicine. A 2006 international consensus statement replaced it, along with related terms like “pseudohermaphrodite,” with “disorders of sex development” (DSD). The older language was considered inaccurate, confusing, and stigmatizing to patients and families. The newer classification also better reflects what scientists now understand about the genetics and hormones involved. You’ll still see the word “intersex” used by advocacy groups and in everyday conversation, but in clinical settings, DSD is the standard term.
The Rarest Form: Ovotesticular DSD
What people typically picture when they hear “hermaphrodite” is a person born with both male and female reproductive tissue. This condition, now called ovotesticular DSD, is the rarest of all disorders of sex development. A baby with this condition may have an ovary on one side and a testis on the other, or a combined organ called an ovotestis that contains both types of tissue. The genitalia are typically ambiguous at birth, meaning they don’t clearly appear male or female.
Fewer than 1 in 20,000 people are born with ovotesticular DSD. To put that in perspective, in a country the size of the United States, that would mean roughly 16,000 people. Only around 500 cases have been formally reported in the medical literature, though the actual number of living individuals is likely higher since not every case gets published.
The Wider Spectrum of Intersex Conditions
Ovotesticular DSD sits at one end of a much broader spectrum. Many other conditions affect how sex characteristics develop, and they vary widely in how noticeable they are.
Congenital adrenal hyperplasia (CAH) is one of the more common conditions. In its classic form, an enzyme problem causes the adrenal glands to produce excess androgens (hormones that drive male-typical development). Girls born with classic CAH may have genitalia that appear partly masculinized, while the internal reproductive organs are typically female. Classic CAH occurs in about 1 in 15,000 to 20,000 births. A milder, “non-classic” form that usually doesn’t cause visible genital differences affects roughly 1 in 1,000 people overall, and as many as 1 in 100 to 200 in certain ethnic groups.
Androgen insensitivity syndrome (AIS) works in the opposite direction. A person with complete AIS has XY chromosomes and internal testes, but their body cannot respond to androgens. They develop female external anatomy and are typically raised as girls, often not learning about the condition until puberty, when periods don’t start. Complete AIS affects 2 to 5 in every 100,000 people born with XX-typical appearance. Partial AIS, where the body responds to some but not all androgens, is thought to be at least as common.
Chromosomal variations add another layer. Klinefelter syndrome, where a person is born with an extra X chromosome (47,XXY instead of the typical 46,XY), occurs in roughly 1 in 500 to 1,000 male births, making it one of the most common chromosomal conditions in humans. Most people with Klinefelter syndrome look and identify as male, though they may have reduced fertility and other subtle differences. Turner syndrome, where a person has only one X chromosome (45,X), occurs in about 1 in 2,500 female births.
Why Prevalence Estimates Vary So Much
You’ll often see two very different numbers cited for how common intersex conditions are: 1.7% and 0.018%. The gap between them is almost entirely about where you draw the line.
The 1.7% figure comes from biologist Anne Fausto-Sterling, who added up every condition that causes any deviation from typical male or female development. That includes Klinefelter syndrome, Turner syndrome, non-classic CAH, and other conditions where a person may never know they have anything unusual without genetic testing. Under this definition, intersex is about as common as red hair.
The 0.018% figure comes from a response by Leonard Sax, published in the Journal of Sex Research, who argued that intersex should only include conditions where a person’s chromosomal sex clearly conflicts with their physical appearance, or where the body can’t be easily classified as male or female. By that stricter definition, intersex is about as common as albinism. That’s roughly 1 in 5,500 people.
Neither number is wrong. They’re answering different questions. If you’re asking how many people are born with bodies that visibly don’t fit male or female categories, the smaller number is closer to reality. If you’re asking how many people have some biological variation in their sex chromosomes, hormones, or anatomy, even variations they might never notice, the larger number is more accurate.
How These Conditions Are Discovered
Some intersex conditions are obvious at birth. A baby with ambiguous genitalia will typically undergo evaluation in the first days of life, including hormone testing and imaging. Ovotesticular DSD and classic CAH are usually identified this way.
Other conditions don’t become apparent until puberty. A teenager with complete AIS may see a doctor because menstruation never starts. Someone with Klinefelter syndrome might not be diagnosed until adulthood, often during a fertility workup. In fact, many chromosomal variations are never diagnosed at all. An estimated 75% of people with Klinefelter syndrome go through life without knowing they have it.
This gap between conditions that are visible at birth and those that are discovered later (or never) is a major reason the prevalence question is so hard to pin down. The rarest and most dramatic presentations get the most attention, but the subtler variations are far more common and largely invisible.