A gender role is a set of norms, or culturally defined expectations, that specify how people of one gender ought to behave. Children are socialized into gender roles first by parents and later by other forces such as peers and the media.

Gender roles are not uniform in the United States. They vary according to ethnic group and other factors. African American women, for example, have traditionally played an important economic role in their families. Among Latinos, gender roles tend to be more sharply defined than they are among Anglos. The sexuality of Asian Americans has been stereotyped, with Asian American men seen as being sexless and Asian American women viewed as exotic sex toys. Some American Indian tribes traditionally had egalitarian gender roles compared with white culture.

Psychological gender differences have been documented in aggressiveness and communication styles.

The two largest male-female differences in sexuality are in the incidence of masturbation (males having the higher incidence) and attitudes toward casual sex (females being more disapproving). Heiman's study of arousal to erotic materials illustrates how males and females are in some ways similar and in others different in their responses. Males are more consistent at having orgasms, especially during heterosexual intercourse, than females are, and males have a somewhat stronger sex drive.

Three sets of factors have been proposed to explain gender differences in sexuality: biological factors (anatomy, hormones); cultural factors (gender roles, the double standard); and other factors (fear of pregnancy, differences in masturbation patterns creating other gender differences).

Most research on gender and sexuality has been done with college-age samples. There is reason to believe that patterns of gender differences in sexuality change in middle age and beyond.

Transsexuals represent an interesting variation in which gender identity does not match anatomy. Generally, their adjustment is good following the gender-reassignment operation. Transgender is a broader category including those who do not seek surgery or see themselves as being in a third gender category.