Transmission of human immunodeficiency virus (HIV) is known to occur perinatally, through sexual contact, and after exposure to infected blood or blood products. The possibility that breast milk may transmit HIV continues to be evaluated. There is no epidemiologic evidence that contact with saliva, tears, or urine has resulted in HIV infection. However, because HIV has (in some cases rarely) been isolated from these body fluids, guidelines have been developed to reduce more extensive exposures to such secretions. Laboratory and epidemiologic data strongly indicate that HIV is not transmitted through immune globulin preparations, the hepatitis B vaccine, or contact with insects. Increasing evidence from many studies also indicates that HIV is not transmitted through casual contact. All individuals need to be aware of how HIV is and is not transmitted, to reduce high-risk behaviors and to avoid unnecessary fears and actions.