The Olympic Games mandates sex verification of athletes in women's competitions, and has done since the 1930s. In this time, there have been many different regulations for sex testing, as well as different types of tests used. Initial concerns that prompted the approval of suspicion-based sex testing were of national teams exploiting intersex athletes for Olympic success, and testing first became a requirement in the 1960s when many female athletes were doped and it was harder to tell physical differences between them and men.
In its history, different sex testing methods at the Olympics have been known to produce false positive and false negative results, incorrectly excluding some biological women. No "male imposters" have ever been identified through sex testing. The International Olympic Committee re-confirmed the use of sex verification in several meetings in the 1980s and 1990s, each time confirming its use for preventing "male imposters", and not aiming to exclude intersex women.
Sex testing at the Olympics has been criticised for a variety of reasons, and briefly stopped. Various international medical and sports professionals have advocated for the abolition of sex verification in sport, and specifically the Olympics.
Regulations and methods of sex verification.
Introduction of regulations.
Women first competed at the Olympic Games in 1900, with an increased programme available for women to enter from 1924. Prior to 1936, sex verification may have been done "ad hoc", but there were no formal regulations;"" the existence of intersex people was known about, though, and the Olympics began "dealing with" – acknowledged and sought to regulate – intersex athletes ahead of the 1936 Games, following the case of intersex athlete Zdeněk Koubek becoming globally known in 1935.""
History of regulations and tests.
1936–1966: Physical examination in cases of doubt.
After Zdeněk Koubek, a Czech athlete raised as a woman, was identified as intersex and transitioned to live as a man in 1935, then-United States Olympic Committee (USOC)-president Avery Brundage expressed concern over the potential for such athletes to be exploited for Olympic gain. The USOC requested the International Olympic Committee (IOC) to permit medical examinations of any athletes whose sex was questioned, which became policy in time for the 1936 Summer Olympics. It did not appear to be applied in 1936, though there were some notable cases in the form of Stella Walsh and Heinrich Ratjen. Walsh's case was handled sympathetically, while Ratjen's Olympics appearance may have been deliberately dishonest.
Walsh and her American rival Helen Stephens were accused of being men by other competitors in 1936, and Stephens' gender was questioned by Polish media disgruntled that the Poland-born Walsh had been beaten by her. At the Olympics, Stephens said that Adolf Hitler (who was overseeing the Games) groped her as a joke to check; Stephens later took and passed a gender test. Upon Walsh's death in 1980, however, it was discovered that Walsh was intersex, though it was also determined she likely never knew.
Ratjen, who was raised female, was never tested during sporting events, but suspicion over his gender was widespread. He was publicly accosted before being forced to strip and then arrested in 1938, also made to assume a male identity. Having competed for Nazi Germany in 1936, he later claimed that his country had noticed his biological difference and made him compete as a woman in order to win for them.
International sports was disrupted by World War II, and the requirement for female athletes to show a medical certificate proving their sex at competition was introduced by 1946. There was no universal standard of testing, however, with sporting bodies allowing whichever nation or medical professional had produced an athlete's certificate to use their own definition of "femininity".
1967–1991: X-Chromatin testing for all women participants.
Trusting an athlete's nation to be medically accurate ended in the 1960s, however, and sports federations began regulating "femininity". In the 1960s, when systemic doping became a significant issue and it was harder to tell the difference between men and doped women, formal sex verification was first implemented as a requirement: between 1968 and 1998, all female athletes at the Olympics were subject to sex verification as a matter of process. Testing as a requirement had been gradually introduced at other events in 1966 and 1967, some of which still used the previous invasive physical examinations. An early test at the 1967 European Cup incorrectly identified Ewa Kłobukowska as not female, seeing her previous Olympic achievements written off and her career end. Kłobukowska is missing an X chromosome, a genetic disorder that does not make her intersex or biologically male. However, the test being used – and which would officially be used for the next 25 years – was for identifying Barr bodies, a sign of the presence of two (or more) X chromosomes. Kłobukowska had previously passed the sex test at a competition in 1966, which should have permitted her to compete in future. The Barr body test was first trialled by the IOC at the 1968 Winter Olympics, where Erik(a) Schinegger's intersex condition was discovered and he was removed from participation, before being implemented at the 1968 Summer Olympics.
There was one known exception of a female Olympic athlete who was not subject to sex verification: Anne, Princess Royal, who competed in 1976. Considered unnecessary for such a public figure, Anne also competed in equestrian eventing – which features teams of four riders of any sex. 
The test to identify multiple X chromosomes had already been considered unreliable in the scientific community for decades, which stopped using it by 1970, but remained widespread in sports until 1992. In this time, the test incorrectly banned at least one other female athlete in addition to Kłobukowska: Maria José Martínez-Patiño, who was banned after she qualified for the 1988 Summer Olympics, before being reinstated later in 1988 after these Games took place.
1992–1996: SRY testing for all women participants.
Ahead of the 1992 Winter Olympics, the Olympics stopped using the X-Chromatin tests. The Olympics initially replaced the X chromosome test with an SRY test, relating to a gene of the Y chromosome. Later in 1992, other sports federations, including the IAAF (now World Athletics), stopped all sex testing unless suspicion arose; IAAF events included drug testing through athletes producing a urine sample while visible to the medics, which was suggested to effectively serve as a visible sex confirmation and prevent the need for testing. Five sports federations, including judo and volleyball, continued requiring sex verification. At the same time, the Olympics decided to permit the participation of female athletes who had undergone "sex reassignment surgery", two years after their surgery and predicated on meeting the typical requirements.
The SRY test was used for all athletes at the 1996 Summer Olympics. Prior to the 1996 Games, intersex Brazilian judoka Edinanci Silva had surgery to allow her to continue in women's sport – going on to compete at four Olympics – while Philippine sprint hopeful Nancy Navalta was tested and ruled intersex, being removed from her delegation for the Games. There were eight (unknown) female athletes competing in 1996 who were discovered to have an intersex condition upon testing. All had full or partial androgen insensitivity, and all were allowed to compete. In 1999, the IOC abolished the universal testing so as to protect the dignity of athletes who do not already know they have these conditions.
1999–2019: Reversion to suspicion-based testing.
In the late 1990s, there was major pushback against sex verification among relevant professional bodies, including the American Medical Association; among the criticisms was the SRY test not producing reliable results. Starting with the 2000 Summer Olympics, the IOC stopped testing all female participants, but continued to perform sex testing for athletes of any gender (though invariably women) when "serious doubts" were raised. In the 21st century, it also stopped using chromosome screening for tests. 
Following various changes in policy by other sporting bodies at the start of the 21st century, the IOC issued new guidance ahead of the 2012 Summer Olympics, focusing on cases of hyperandrogenism and so testing for testosterone. Such tests were still done only by request, and were also deemed unreliable and discriminatory, especially considering the effects of androgen insensitivity. The increased concern regarding testosterone had begun with the IAAF investigating Caster Semenya after her success at the 2009 World Championships in Athletics. In 2015, however, testosterone testing had to be suspended following a legal case brought by Dutee Chand in the Court of Arbitration for Sport (CAS), which ruled that there was insufficient proof of any advantage to discriminate against all women with hyperandrogenism.
Immediately prior to the 2016 Olympic Games and in response to sex verification controversies, Myron Genel, Joe Leigh Simpson and Albert de la Chapelle in the "Journal of the American Medical Association" stated "One of the fundamental recommendations published almost 25 years ago ... that athletes born with a disorder of sex development and raised as females be allowed to compete as women remains appropriate".
In 2017, in response to the CAS ruling on Chand's case, a study was published that analysed athletic performance and hormone concentrations. It concluded that female athletes with high testosterone levels have a significant competitive advantage over those with low testosterone levels in 400 m, 400 m hurdles, 800 m, hammer throw, and pole vault.
In 2018, World Athletics began requiring intersex women to medically or surgically alter themselves in order to be eligible, which could prevent them from attending events that serve as Olympic qualifiers. Semenya has refused to take hormone medication, which saw her banned from participation.
Criticisms.
Various international medical and sports professionals have, since 1986, advocated for the abolition of sex verification in sport, and specifically the Olympics. In 2000, following the 1999 IOC ratification of the 1996 decision to discontinue sex verification, the view was reiterated in the "Journal of the American Medical Association"; it included commentary that, while the purpose of such tests is to uphold a perceived fairness, the insufficiency of the tests can produce unfair results due to potential inaccuracies and the possibility of both false negatives and false positives. The authors also deemed the tests unfair and discriminatory towards female athletes with disorders of sex development (DSD), whom it felt should be considered as women for the purposes of sport, as "few if any plausible athletic advantages exist". It also considered the implications for female athletes who "fail" a test (either as an error or through unknowingly having a DSD), in their personal lives and future career, as too severe to impose the tests.
For several years, sex testing used a suspicion-based approach, which has been criticised as it enables racist discrimination.
In 2022, the World Medical Association (WMA) demanded the withdrawal of hormone-based regulations, arguing that they discriminate based on gender variation of female athletes. The Association also expressed concerns with physicians treating athletes with high levels of endogenous testosterone when the condition is not pathological.
Other criticisms are that there is no natural physiological limit imposed on male athletes, including those who have, for example, naturally high testosterone compared to their competitors, and that there are many biological factors that produce sporting advantages but "only those associated with gender are used to exclude or disqualify athletes."
List of intersex Olympic athletes.
Identification.
This list includes athletes who have competed at the Olympic Games, or were set to compete at the Olympic Games, and who have a known intersex (disorders/differences of sex development; DSD) condition and this is publicly known. The 1932 Summer Olympics was the first instance of an athlete now known to be intersex competing at the Olympics. The majority of intersex Olympians have competed in athletics, generally running.
In its history, different sex testing methods at the Olympics have been known to produce false positive and false negative results, incorrectly excluding some biological women. The athletes listed may or may not identify as intersex or having a DSD.
Athletes with a DSD may be known as intersex, with the terms often understood interchangeably; the term "hermaphrodite" is now widely discredited. DSDs are congenital conditions affecting the reproductive system, in which development of chromosomal, gonadal, or anatomical sex is atypical. As a biological status, intersex people may identify as heterosexual and cisgender. While intersex people face specific issues that LGBT+ people do not, in sports they are often considered alongside transgender athletes who have transitioned, with similar barriers to participation.
Overview.
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Key.
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