In 1990, nearly 1.5 million human immunodeficiency virus (HIV) antibody tests were performed at publicly funded sites. Eight percent of those tests were performed for self-identified illegal injecting drug users (IDU). The authors examined data from 28 project areas using a client record data base that permitted an analysis of self-reported risk behavior by type of service delivery site. Among self-identified IDUs, 68 percent of those tested and 82 percent of those found to be seropositive had obtained HIV counseling and testing services in settings other than drug treatment centers. The findings indicate that HIV-prevention programs for IDUs need to be available in various service delivery settings, not just in drug treatment programs. Strong links and cooperation between sites offering HIV counseling and testing and sites providing drug treatment programs are important to preventing HIV transmission to and from IDUs.