HIV infection can be transmitted through all types of unprotected sexual intercourse (oral, vaginal and anal) in which infected bodily fluids or secretions can come into contact with mucous membranes. The risk is highest in unprotected anal sexual intercourse with an infected person and lower in vaginal intercourse. Unprotected oral intercourse is least risky, but still risky, especially when the mucous membrane in the mouth and throat is wounded (e.g. with bleeding gums, ulcers and throat infections).

The risk is highly (although not absolutely) reduced by consistent and correct use of condoms.

The transmission of HIV infection by kissing has never been proven, although the saliva of an infected person may contain some virus. Nevertheless, there is a theoretical risk involved in deep kissing, especially when the saliva contains blood (e.g., due to bleeding gums).

Masturbation is not risky. Theoretically, one could become infected if genital secretions came into contact with mucous membranes or injured skin.