We assessed human immunodeficiency virus (HIV) antibody prevalence and drug-using behaviors among intravenous drug abusers (IVDAs) enrolled in Milwaukee drug treatment programs. Six (2.3%) of 266 study participants were positive for HIV antibody by Western blot assay. A history of needlesharing was reported by 91% of participants, injection of drugs within the past 6 months by 76%, visits to a shooting gallery by 34%, and drug injection outside of Wisconsin by 41%. Nonwhite participants were more likely than white participants to share needles greater than 5 times per month (odds ratio of 2.0) and more likely to have visited a shooting gallery greater than 5 times (odds ratio of 2.7). The average frequency of injection did not differ significantly by race or gender. Pharmacies were the most frequently listed source of sterile needles, and the most common reason for sharing needles was convenience. We conclude that as of late 1987, HIV seroprevalence in Milwaukee IVDAs remained relatively low compared to that of IVDAs in the northeastern United States. There may be racial differences in drug-using behaviors that define distinct subpopulations of IVDAs. These differences should be assessed further, since they have important implications for the success of AIDS education efforts.