An overwhelming body of evidence demonstrates that condoms are highly effective in preventing transmission of HIV. Correct and consistent condom use should give you a high degree of confidence in your ability to prevent HIV transmission.

At least four different types of evidence demonstrate the effectiveness of condoms in preventing HIV transmission. Laboratory studies have shown that the virus cannot pass through latex or polyurethane. There is also a theoretical basis for effectiveness: condoms prevent exposure to semen or vaginal fluids that may carry the virus. Epidemiological studies, which compare infection rates among condom users and non-users, have found that condoms offer significant protection against HIV infection. Finally, in many countries that have significantly reduced HIV infection rates (such as Brazil, Thailand and the USA), reduced rates of transmission have been strongly associated with increased condom use.

Few prevention methods are 100% effective. Condoms do occasionally slip or break, although fortunately this rarely happens. Condoms that are outdated, poorly manufactured, or inappropriately stored are especially susceptible to breakage. Oil-based products (such as hand lotion or petroleum jelly) can also damage male latex condoms, so only water-based lubricants should be used during sexual intercourse with a male condom.

In general, condoms are most likely to fail when they are not used as directed. Opening a condom packet with your teeth, a knife or scissors, for example, can inadvertently cause the condom to tear. It is important to use condoms from the beginning of a sexual act, rather than just before ejaculation, to prevent exposure to potentially infectious pre-ejaculate or vaginal fluids. Studies suggest that the frequency of condom failure declines as individuals become more accustomed to using condoms. That is one reason why effective HIV prevention includes both accurate information on condoms and measures to increase individual skill in using condoms correctly. As employees of the UN system, we are entitled to a facilitated demonstration of the use of both male and female condoms.

In reality, condoms are extremely effective in preventing HIV transmission when they are used. Because sexual intercourse is often unplanned, it is a good idea to always carry a condom in case you need one. If you have a steady partner, you should also discuss how you as a couple intend to reduce the risk of HIV transmission.

Ideally, a couple's decision to use a condom results from a process of negotiation. The couple discusses the benefits of using a condom, addresses any concerns or resistance, and agrees on a mutually satisfactory approach. Sometimes, though, one member of the couple may lack the power to negotiate condom use. Many women, for example, report having difficulty asking their husband or partner to use a condom.