In 1981, clinicians and epidemiologists recognized the occurrence of a new syndrome since termed acquired immunodeficiency syndrome (AIDS).1,2 Since then, parenteral and sexual transmission of an agent were implicated.3,4 The subsequent discovery of human immunodeficiency virus type 1 (HIV-1) as the cause of AIDS, and tests for its reliable detection, revealed epidemic spread of this infectious agent that was more extensive and initially more silent than most observers had guessed.5-7
Intensive epidemiologic studies of homosexual men, hemophiliacs, and blood transfusion recipients have been numerous and revealing.4 Analogous research efforts among drug abusers have been somewhat slower to bear fruit.8 In part, this reflects the challenges faced by researchers in enlisting representative samples of drug abusers. Drug abusers are frequently suspicious of "the establishment" and researchers can be perceived as being part of that establishment. Trained interviewers and attention to confidentiality are integral components in obtaining