Societies differentiate among their members not only according to wealth, power, and status, not only according to race, ethnicity, and religion, but also according to age, gender, and sexual orientation. In every society, each age group and each gender is assigned different duties, responsibilities, privileges, and roles. Some of this differentiation is a result of common sense. In the United States, young people cannot drive before they are 16, they cannot vote before they are 18, and they cannot run for the Senate before they are 30. These age restrictions have been set by law on the basis of the belief that people are too immature to engage in these activities at younger ages. On a more informal basis, a person in his seventies would hardly be expected to work on the construction of a 30-story office building, nor has it been thought fit, throughout human history, to have women in charge of protecting societies by going to war. Women’s biological role in reproduction made them too precious to be allowed to be killed in war. Similarly, prohibitions against homosexuality can also be thought of as based on a societal fear that not enough new members will be produced if sex is not strictly heterosexual. In other words, to a certain degree, age, gender, and sexuality differentiation is based on what works best for society. Still, differentiation and the consequent stratification always imply inequality, and it is this factor that this chapter examines.