Repeated ( > or = two visits) emergency department (ED) visits by HIV-infected (HIV+) drug users in New York State (NYS) vary widely by region and may reflect regional inequities in receipt of needed drug treatment and medical services. The study's objective was to evaluate receipt of drug treatment and medical care by HIV+ drug users by region and its effect on ED use. For NYS Medicaid-enrolled HIV+ drug users (N = 11,556) in 1996 and 1997, we identified receipt of long-term (> or = six months) drug treatment, HIV care, and a usual source of medical care from claims files. Regions were classified as New York City, downstate suburban, upstate urban, and rural/small city. We examined adjusted associations of these services with > or = two ED visits in the entire cohort and separately among patients who do and do not receive these three types of services. Repeated ED visits were greatest in rural/small cities (40.7 percent) and least in New York City (24.1 percent; p < 0.001), and receipt of drug treatment was also poorest (p < 0.001) in rural/small cities, whereas receipt of HIV care and usual source of medical care varied less by region. Adjusted odds of > or = two ED visits was increased for patients in rural/small cities (1.89 [confidence interval, 1.44 to 2.50]) vs. New York City and reduced for patients with long-term drug treatment (0.76 [confidence interval 0.69 to 0.84]). Among persons receiving long-term drug treatment, observed regional differences in ED use largely disappeared. Regional variations in receipt of long-term drug treatment by HIV+ drug users in one state appear to contribute to large differences in ED utilization.