Relatively little is known about sexual dysfunction (SD) in men who have sex with other men (MSM). In 2004–2005, an internet sample of American MSM was recruited from gay-oriented networking, chat, and sexual news websites. The analytical sample included 7001 men aged 18 or older who reported having male sexual partners throughout their lives and having had oral or anal sex with a male partner in their most recent encounter in the past year (Mao J Sex Med 6:1378–1385, 2009). Overall, 79% of men reported one or more symptoms of SD in the past year, with low sexual desire, erection problems, and performance anxiety being the most common. Four distinct underlying patterns of sexual functioning were identified through LCA: low SD, erection/performance anxiety problems, low desire/pleasure, and high SD/sexual pain. High SD/sexual pain were distinguished from other patterns by the use of club drugs and the use of prescription and over-the-counter erectile dysfunction drugs before sex in the past year. In addition, men associated with the high SD/sexual pain group were younger, single, more likely to have poor mental and physical health, and more likely to have received a diagnosis of sexually transmitted infection in the past year compared to men in the no/low SD group (Hirshfield J Sex Med 7:3104–3114, 2010).