Among laypersons and even among scientists, little agreement exists about the definition of sex. Using the prototype approach, the current research explored the prototypical structure of sex. Further, it examined important intersexual and intrasexual personal templates. In Study 1, 122 participants produced a list of 80 features for the concept sex, which were rated for typicality by 251 participants in Study 2. Important sex differences with respect to the prototype of sex and correlations with sociosexual orientation were also revealed in Study 2. Study 3 (n = 98) extended these findings by showing that response latencies differ for central versus peripheral features, women versus men, and depend on the sociosexual orientation of the participants.