within each of these groups related to, for example, race, ethnicity, socioeconomic status, geographic location, and age also are addressed later in the chapter.)

Lesbians, gay men, and bisexual men and women are defined according to their sexual orientation, which, as discussed in Chapter 2, is typically conceptualized in terms of sexual attraction, behavior, identity, or some combination of these dimensions. They share the fact that their sexual orientation is not exclusively heterosexual. Yet this grouping of “nonheterosexuals” includes men and women; homosexual and bisexual individuals; people who label themselves as gay, lesbian, or bisexual, among other terms; and people who do not adopt such labels but nevertheless experience same-sex attraction or engage in same-sex sexual behavior. As explained throughout the report, these differences have important health implications for each group.

In contrast to lesbians, gay men, and bisexual men and women, trans-gender people are defined according to their gender identity and presentation. This group encompasses individuals whose gender identity differs from the sex originally assigned to them at birth or whose gender expression varies significantly from what is traditionally associated with or typical for that sex (i.e., people identified as male at birth who subsequently identify as female, and people identified as female at birth who later identify as male), as well as other individuals who vary from or reject traditional cultural conceptualizations of gender in terms of the male–female dichotomy. The transgender population is diverse in gender identity, expression, and sexual orientation. Some transgender individuals have undergone medical interventions to alter their sexual anatomy and physiology, others wish to have such procedures in the future, and still others do not. Transgender people can be heterosexual, homosexual, or bisexual in their sexual orientation. Some lesbians, gay men, and bisexuals are transgender; most are not. Male-to-female transgender people are known as MtF, transgender females, or transwomen, while female-to-male transgender people are known as FtM, transgender males, or transmen. Some transgender people do not fit into either of these binary categories. As one might expect, there are health differences between transgender and nontransgender people, as well as between transgender females and transgender males.

Whereas “LGBT” is appropriate and useful for describing the combined populations of lesbian, gay, bisexual, and transgender people, it also can obscure the many differences that distinguish these sexual- and gender-minority groups. Combining lesbians and gay men under a single rubric, for example, obscures gender differences in the experiences of homosexual people. Likewise, collapsing together the experiences of bisexual women and men tends to obscure gender differences. Further, to the extent that lesbian, gay, and bisexual are understood as identity labels,