One of the major risk behaviors for infection by the HUMAN IMMUNODEFICIENCY VIRUS (HIV) is injecting drug use; the others are unprotected male homosexual sex (Centers for Disease Control, 1991a) and unprotected heterosexual sex with an HIV-infected partner. The NATIONAL INSTITUTE ON DRUG ABUSE (NIDA) estimated that there were between 1.1 and 1.3 million injecting drug users (IDUs) in the United States in the late 1980s (Centers for Disease Control, 1987). Although the number of IDUs increased between 1990 and 1997, participation in needle exchange programs also increased, as did participation in HIV testing and counseling (Des Jarlais et al., 2000).

In 1990, 30 percent of ACQUIRED IMMUNODEFICIENCY SYNDROME (AIDS) cases were heterosexual injecting drug users; in addition, 30 to 50 percent of new cases identified were related to IDU (Iguchi et al., 1990). Injecting drug use was also related to most instances of heterosexual transmission of the virus (Centers for...