According to amfAR, The American Foundation for AIDS Research, "When male condoms are used correctly and consistently, they are 80-95% effective in reducing the risk of HIV infection." amFar: "The Effectiveness of Condoms in Preventing HIV Transmission"
The virus is much more easily transmitted where there are interruptions in the integrity of the tissue surface -- i.e. Tears. Rectal tissue tears more easily than vaginal, and that's why transmission rates are three to twenty times higher for the receptive partner in (gay or straight) anal sex with ejaculation than for a woman … Read more