In Vancouver, British Columbia, Canada, difficulty accessing syringes at night has been shown to be strongly associated with human immunodeficiency virus (HIV) risk behavior among the city's injection drug users (IDUs). On September 1, 2001, the Vancouver Area Network of Drug Users (VANDU) initiated an unsanctioned all-night needle-exchange program on a street corner in the heart of the neighborhood where many of the city's IDUs are concentrated. An external evaluation of the population reached by the VANDU exchange was performed through the Vancouver Injection Drug User's Study, a prospective cohort study of IDUs begun in 1996. Persons accessing syringes through the exchange were compared to those active injectors who acquired their syringes from other sources, including the city's fixed site exchange, which closes at 8:00 PM. Overall, 587 active IDUs were seen during the period September 2001 to June 2002; of these individuals, 165 (28.1%) reported using the VANDU exchange. In multivariate analyses, participants who used the VANDU table were more likely to frequently inject cocaine (adjusted odds ratio [AOR]=1.56; 95% confidence interval [CI]=1.00-2.44), inject in public (AOR=2.71; 95% CI=1.62-4.53), and require help injecting (OR=2.13; 95% CI=1.33-3.42). Interestingly, use of the table was also independently associated with safer syringe disposal (AOR=2.69; 95% CI=1.38-5.21). Results indicate that the unsanctioned exchange appears to have reached those IDUs at highest risk of HIV infection. Although the cross-sectional nature of the study design warrants caution, we also found that use of the nighttime exchange was strongly associated with higher rates of safe syringe disposal. The data suggest that drug user organizations can play a major role in reducing harm among their peers by reaching the highest risk drug users with harm reduction services. The findings also suggest that other forms of syringe-exchange programs should consider the benefits of offering fixed site nighttime service.