Increasing intravenous drug users' (IVDUs) knowledge about the etiology and symptoms of the human immunodeficiency virus is a first step in controlling the spread of the virus to the general population. A comparison of pretest and posttest measures of knowledge of acquired immune deficiency syndrome among IVDUs participating in an AIDS education program reveals significant increases in knowledge after a basic one-hour education session. Additional analyses indicate that IVDUs are more ignorant of certain aspects of AIDS than others, and frequently less amenable to education efforts related to these aspects. Finally, the analyses show that the knowledge among IVDUs about AIDS is independent of the IVDU's demographic characteristics and risk-profile.