FOR NEARLY 15 YEARS, WE HAVE ADVOCATED ABOLItion of laboratory-based, on-site testing for gender verification in sports competition. The ostensible goal of gender verification is to ensure that female athletes do not unwittingly compete against men. Given that men presumably would have an unfair competitive advantage on the basis of speed or muscle mass, such a policy superficially seems endorsable on the grounds of fairness. In reality, gender verification tests are difficult, expensive, and potentially inaccurate. Furthermore, these tests fail to exclude all potential impostors (eg, some 46,XX males), are discriminatory against women with disorders of sexual development, and may have shattering consequences for athletes who “fail” a test. During the 1996 International Olympic Committee (IOC) World Conference on Women and Health, the IOC passed a resolution “to discontinue the current process of gender verification during the Olympic Games.” In January 1999 the IOC Athletes’ Commission recommended to the IOC Executive Board that gender verification testing be discontinued, and the decision was ratified in June 1999 by the 109th IOC session in Seoul, South Korea. The medical community should applaud the decision of the IOC to abolish onsite gender verification preceding athletic events, effective with the current Summer Olympics in Sydney, Australia. The issue of gender verification arose in the early 1960s when rumors circulated that men secretly posing as women were competing against female athletes. At the 1966 European Track and Field Championships in Budapest, Hungary, and at the 1967 Pan American games in Winnipeg, Manitoba, physical inspection was made of disrobed female athletes. At the 1966 Commonwealth Games in Kingston, Jamaica, gynecologic examinations were performed. Complaints and resentment about this embarrassing approach led the IOC to search for an alternative gender verification method at its competitions. The IOC decided to require all female athletes to undergo sex chromatin analysis (X chromatin or Barr body analysis). Laboratory-based gender verification became compulsory in 1968 at the Mexico City Summer Olympics, after it was introduced on a small scale at the European Cup in Track and Field Athletics in Kiev, Ukraine (1967) and the Grenoble Winter Olympics (1968) in France. Gender verification has long been criticized by geneticists, endocrinologists, and others in the medical community. One major problem was unfairly excluding women who had a birth defect involving gonads and external genitalia (ie, male pseudohermaphroditism). Male pseudohermaphroditism is defined as genetic males (Y chromosome) whose external genitalia fail to develop—the genitalia may be ambiguous or resemble female genitalia. Many different forms of male pseudohermaphroditism exist. A second problem is that only women, not men, were stigmatized by gender verification testing. Systematic follow-up was rarely available for female athletes “failing” the test, which often was performed under very public circumstances. Follow-up was crucial because the problem was not male impostors, but rather confusion caused by misunderstanding of male pseudohermaphroditism. Noteworthy was the courageous contribution of the Spanish hurdler Maria Martinez Patino in documenting abuse by sports authorities. Patino had complete androgen insensitivity, and like most male pseudohermaphrodites she was raised as female. If athletic, these individuals naturally compete as women. Few if any plausible athletic advantages exist, especially given that gonadal extirpation usually has occurred by adulthood; however, abnormalities in external genitalia and gonads understandably create confusion.