This chapter analyzes transgender participation in elite competition sports with special emphasis on Male-To-Female who have hormonally transitioned. Social and legal discrimination of transgender individuals and the legal restrictions on the recognition of the change of sex prevented any transgender athlete from being eligible by sports authorities for a sexual category that was not congruent with the biological one. The underlying goal of sex-segregated competition is purportedly to establish a fair competition given that alternative of a competition without sex segregation would put women at a disadvantage. Sex categorization, from a medical perspective, is simultaneously ideological in that there are vast differences between members of one sex; in that there exists a mean average difference between males and females. The shift, from a medical perspective, with search for genetic diagnosis to a sports-related perspective for the best biological marker eventually lead to the end of gender verification policies.