Men who have sex with men

Men who have sex with men (MSM) is a classification of men who engage in sex with other men, regardless of whether they identify themselves as homosexual/gay, bisexual, or heterosexual. The term is intended to reference a particular category of people as a risk-group for HIV, and is considered a behavioural category.

As this label can only be reliably applied where the sex of individuals is unambiguous, it is not used for transsexuals, transgendered individuals and intersexuals, except in cases where it is clear that they engage in risk behaviors similar (or equivalent) to the risk behaviors of unambiguous men having sex with unambiguous men. Because risk factors vary between cultures, the category is not used for cases in which this specific risk behavior is no longer a significant category for the contraction of HIV or other STDs.

MSM groups include:
 * Sexually active gay males
 * Bisexual males sexually active with other males
 * Men on the down-low with other men
 * Anonymous (or faceless) sexual encounters between men such as at glory holes
 * Male sex workers (commercial or not) with male clients

MSM as behavioural category
Young and Meyer (2005) note that the term has been in use within the public health discourse since 1990 or earlier, but that the coining of the initialism by Glick et al. (1994) "signaled the crystallization of a new concept." They trace the emergence of this behavioural concept to two very distinct academic perspectives. First, it was pursued by epidemiologists seeking behavioural categories that would offer better analytical concepts for the study of disease risk than identity-based categories (such as "gay", "lesbian", or "straight", because a man who self-identifies as gay or bisexual is not necessarily sexually active with men). Second, its usage could in part be explained by the criticism of sexual identity terms prevalent in the "social construction" literature, which typically rejected the use of identity-based concepts across different cultural and historical contexts.

MSM as a construct
As a risk category, MSM are not limited to small self-identified and visible sub-populations, such as gay men and male sex workers. "MSM" and "homosexual" refer to different social identities. "MSM" refers to the sexual relationships between men, whether or not they identify as homosexual, or bisexual. "Homosexuality" refers to more than the sexual relationship and may extend to broader relationships with the same sex, i.e., lifestyle, sexuality, etc.

In their assessment of the knowledge about the sexual networks and behaviours of men who have sex with men in Asia, Dowsett, Grierson and McNally observed that using MSM as a category does not always work. From the material they have reviewed there is not any clearly identifiable group of men who can be labelled MSM in any of the countries that they investigated.

"'The literature reveals that there are no socially or self-defined groups of men that fit into an overarching category of MSM. What the review shows is that there are just men!! Fishermen, students, factory workers, military recruits, truck drivers, and men who sell sex, and so on: all these categories of men are to be found in the studies and programmes reviewed.'"

There were no similar traits in all of the MSM population studied other than them being males, and engaging in sex with other men.

Non-exhaustive list of people who are not MSM

 * Any woman, including post-operative male-to-female transsexuals, regardless of any other factors
 * Men, including female-to-male transsexuals, who engage in sex exclusively with women, regardless of any other factors
 * Any intersexual person, who does not engage in risk behaviors similar or equivalent to sex between MSM, regardless of self-identity, genital appearance, or social assignment
 * Any transgender or transsexual individual, who does not engage in risk behaviors similar or equivalent to sex between MSM, regardless of self-identity, genital appearance, or social assignment
 * A man who participates in a sexual act with another person, unknowing that their partner may otherwise satisfy some particular individual criteria typically asserted to be exclusive to males (for example: genetically, a woman with Androgen Insensitivity Syndrome; genitalia: a pre-op transsexual; gonads/hormones: transgender individual)

MSM and HIV/AIDS
In many developed countries AIDS is more prevalent among MSM than among the general population. In the United States, MSM accounted for 49 percent of new HIV diagnoses reported in 2005. One reason for higher prevalence is that engaging in receptive anal intercourse carries a higher risk than other forms of penetrative sex. Critics charge that political correctness has led to the association of MSM and HIV being downplayed.