AIDS is a life-threatening infectious disease with a devasting impact on society. When the AIDS virus enters the bloodstream, it attacks certain white blood cells. In response, the body produces antibodies for which there are tests. Once infected, an individual may remain without signs or symptoms, may develop a less serious disease -- AIDS Related Complex, or may develop a full-blown case of AIDS. In AIDS, a weakened immune system leaves the body vulnerable to a host of opportunistic infections and diseases. Although AIDS is a contagious disease, it is not spread by casual contact. The primary means of transmission are sexual contact and the sharing of intravenous drug needle and syringes. Homosexual and bisexual males and intravenous drug users are at greatest risk of infection. Sexual partners of these high-risk individuals and children born to women carrying the virus also are at risk. The most effective ways of avoiding infection and controlling the AIDS epidemic are to avoid promiscuous sexual practices, maintain faithful monogamous sexual relationships, and avoid injecting illicit drugs. Illustrations and listing of additional resources.