Since the turn of the current century, syphilis incidence and prevalence have been increasing more rapidly among men who have sex with men (MSM) than any other US subpopulation, exceeding their previously high rates in the 1970s and 1980s, before the AIDS epidemic. The reasons for these trends are multifactorial and complex, involving individual behavioral, sociocultural, structural, and biological factors, which will be reviewed in this article. Men who have sex with men tend to have more sexual partners than heterosexuals, and engage in practices (e.g., anal sex) that are highly efficient for syphilis transmission and nondetection of primary chancres. In the era of highly active antiretroviral therapy rendering adherent patients noninfectious and the use of preexposure prophylaxis, there is substantially less concern about HIV transmission and acquisition among MSM, resulting in higher levels of condomless sex. The increased concentration of syphilis among black MSM is partially related to assortative mixing, that is, black MSM being more likely to have other black sex partners, as well as decreased access to preventive services and treatment due to economic marginalization, Societal rejection and discrimination may also potentiate factors that may increase sexual risks resulting in syphilis, for example, depression and substance use. The anticipation of experiencing homophobic discrimination in health care settings may lead many sexually active MSM to delay needed screening and treatment, thus being infectious to partners for longer periods than other populations. To effectively control the syphilis epidemic among MSM, scaling up a combination of programs, ranging from enhanced community education to training clinicians and health care systems to provide culturally competent care, will be necessary.