Gay oral

MSM may engage in oral sex, including fellatio, which is using the mouth to stimulate another person's penis or scrotum, and anilingus, which is stimulating someone else's anus using the tongue and lips.

Four out of newly infected gay men in Amsterdam cited oral sex as their riskiest behavior, one out of 50 in Boston, three out of 49 in San Francisco, one out of 41 in a second S.F. study.