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Sexual Agreements: The Backstory

Revisiting couples' rules and understandings about sex with outside partners.

Key points

  • Research is beginning to examine, and challenge, assumptions of monogamy in established relationships.
  • Between 25 and 66 percent of male couples have agreements that in some way permit sex with outside partners.
  • Agreements are good but imperfect predictors of whether relationship partners have sex with others.
  • Non-monogamous agreements can still involve boundaries or limits on acceptable activities.

Sexual agreements are, in many respects, as old as relationships themselves. Marital traditions going back thousands of years across a wide range of cultures and religions in some way dictate the sexual boundaries of a relationship. In many instances and traditions (though not all by any means), the boundary is monogamy—the understanding that neither partner in the relationship will have sex with other people. This is the established marital norm in the US. Sex with an outside partner (typically referred to as adultery or infidelity in legal discussions) is not only grounds for fault-based divorce in about two-thirds of US states (Cornell Law School Legal Information Institute, June 2021), it is actually criminalized (though rarely prosecuted) in most states (Cornell Law School Legal Information Institute, November 2021).

Many of these norms about sexual boundaries are implicitly or explicitly grounded in a heterosexual paradigm. In the past 20 years, researchers have started paying attention to the sexual boundaries set by sexual and gender minority couples.

Why the growing attention?

Research on sexual agreements began to generate interest in the early 2000s. Around that time, research from the Netherlands indicated that many new HIV infections among sexual minority men were being transmitted between main or primary relationship partners—boyfriends, lovers, spouses, and other ongoing or committed partnerships (e.g., Davidovich et al., 2001). A few years later, complimentary estimates from US data suggested that between 35% and 68% of new HIV infections among sexual minority men were transmitted between relationship partners (Goodreau et al., 2012; Sullivan et al., 2009).

With the realization that main partners account for a substantial number of new HIV infections among sexual minority men, understanding how cisgender male couples manage HIV transmission risk became a public health priority. As part of this, researchers became very interested in the agreements couples make about sex with outside partners. Early research in this area answered a few questions.

What kinds of agreements do couples form?

Monogamy, or sexual exclusivity, is not the only boundary couples may decide on (Cain & Starks, 2024). Studies of male couples consistently suggest that between one-quarter and about two-thirds of them have agreed that sex with outside partners is in some way permitted (e.g., Mitchell & Petroll, 2013; Parsons et al., 2013; Sharma et al., 2019; Sharma et al., 2021; Starks et al., 2020; Starks et al., 2019).

Couples that agree to be non-monogamous may still have some rules and boundaries. A few common boundaries have been identified:

  • Sex with outside partners can only happen when both partners in the primary relationship are present. Estimates suggest that between 10% and 45% of male couples limit sex in this way. Sex always involves the primary relationship partners together, but sometimes additional partners are engaged (Mitchell & Petroll, 2013; Parsons et al., 2013; Starks et al., 2020; Starks et al., 2019).
  • Expectations about communication. The most common rules here involve discussing potential sex with an outside partner before it occurs or disclosing it after the fact (Grov et al., 2014).
  • Shared limits. Some couples place limits on people (e.g., no repeat partners or no sex with mutual friends), places (e.g., “you can go to someone’s place to hook up, but you cannot bring someone to ours"), or activities (e.g., “we only have oral–not anal–sex with other people") (Grov et al., 2014).

Why do couples form agreements?

Researchers working in this area were initially focused on sexual agreements as a way of understanding HIV risk and prevention in male couples. One early study went further and examined male couples' motivations for forming a sexual agreement (Hoff et al., 2010). They found that, indeed, one motivation for forming a sexual agreement was HIV prevention; however, it was not the only reason. These couples also indicated that forming a sexual agreement increased their sense of love and trust in the relationship. It reduced the need to keep secrets and facilitated honesty, disclosure, and discussion.

Are agreements actually associated with behavior?

Maybe the most important finding in these early studies of sexual agreements in male couples was that they actually do predict behavior: When male couples agreed to be monogamous, partners were significantly less likely to have sex with outside partners. Single men and those in non-monogamous relationships have comparable rates of sex with outside partners (Parsons et al., 2013; Starks et al., 2020; Starks et al., 2019).

That said, sexual agreements are not perfect indicators of behavior. Some men with monogamous agreements have sex with outside partners (presumably violating their agreement) (Starks et al., 2020; Starks et al., 2019). When they do, they may actually have sex more often then men who are single or who agreed to be non-monogamous (Starks et al., 2020). Likewise, not all men with non-monogamous agreements avail themselves of the freedom to have sex with other partners.

Where do we go from here?

This research on sexual agreements in male couples represents just one starting point. More recent work has looked at factors that predict whether or not partners agree on what their agreement is and whether folks stick to the agreements that they form. In addition, we are beginning to look at sexual agreements in other LGBTQ+ couples and re-examine norms and assumptions of monogamy in heterosexual relationships. There is a lot to unpack here.


Cain, D., & Starks, T. J. (2024). Sexual Agreements and Arrangements. In A. E. Goldberg (Ed.), The SAGE Encyclopedia of LGBTQ+ Studies (2nd ed.): SAGE Publications.

Davidovich, U., de Wit, J., Albrecht, N., Geskus, R., Stroebe, W., & Coutinho, R. (2001). Increase in the share of steady partners as a source of HIV infection: A 17-year study of seroconversion among gay men. AIDS, 15(10), 1303-1308.

Goodreau, S. M., Carnegie, N. B., Vittinghoff, E., Lama, J. R., Sanchez, J., Grinsztejn, B., Koblin, B. A., Mayer, K. H., & Buchbinder, S. P. (2012). What drives the US and Peruvian HIV epidemics in men who have sex with men (MSM)? PLoS ONE, 7(11), e50522.

Grov, C., Starks, T. J., Rendina, H. J., & Parsons, J. T. (2014). Rules about casual sex partners, relationship satisfaction, and HIV risk in partnered gay and bisexual men. Journal of Sex & Marital Therapy, 40(2), 105-122.

Hoff, C. C., Beougher, S. C., Chakravarty, D., Darbes, L. A., & Neilands, T. B. (2010). Relationship characteristics and motivations behind agreements among gay male couples: Differences by agreement type and couple serostatus. AIDS Care, 22(7), 827-835.

Cornell Law School Legal Information Institute. (2021, June). Fault Divorse. Retrieved June 16 from

Cornell Law School Legal Information Institute. (2021, November). Adultery. Retrieved June 16 from

Mitchell, J. W., & Petroll, A. E. (2013). Factors associated with men in HIV-negative gay couples who practiced UAI within and outside of their relationship. AIDS and Behavior, 17(4), 1329-1337.

Parsons, J. T., Starks, T. J., Dubois, S., Grov, C., & Golub, S. A. (2013). Alternatives to monogamy among gay male couples in a community survey: Implications for mental health and sexual risk. Archives of Sexual Behavior, 42(2), 303-312.

Sharma, A., Garofalo, R., Hidalgo, M. A., Hoehnle, S., Mimiaga, M. J., Brown, E., Thai, J., Bratcher, A., Wimbly, T., Sullivan, P. S., & Stephenson, R. (2019). Do male couples agree on their sexual agreements? An analysis of dyadic data. Archives of Sexual Behavior, 48(4), 1203-1216.

Sharma, A., Kahle, E., Sullivan, S., & Stephenson, R. (2021). Sexual agreements and intimate partner violence among male couples in the U.S.: An analysis of dyadic data. Archives of Sexual Behavior, 50, 1087-1105.

Starks, T. J., Jones, S., Kyre, K., Robles, G., Cain, D., Jimenez, R., Stephenson, R., & Sullivan, P. (2020). Testing the drug use and condomless anal sex link among sexual minority men: The predictive utility of marijuana and interactions with relationship status. Drug and Alcohol Dependence(216), 108318.

Starks, T. J., Robles, G., Bosco, S. C., Dellucci, T. V., Grov, C., & Parsons, J. T. (2019). The prevalence and correlates of sexual arrangements in a national cohort of HIV-negative gay and bisexual men in the United States. Archives of Sexual Behavior, 48(1), 369-382.

Sullivan, P. S., Salazar, L., Buchbinder, S., & Sanchez, T. H. (2009). Estimating the proportion of HIV transmissions from main sex partners among men who have sex with men in five US cities. AIDS, 23(9), 1153-1162.

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