What predicts which metropolitan areas in the USA have syringe exchanges?

HIV epidemics among IDUs vary widely across different cities in the USA [American Journal of Public Health 86 (5) (1996) 642]. Few studies have focused on how localities differ in regard to response to the HIV epidemic. While syringe exchange programmes (SEPs) are a response to HIV among IDUs, they are often unwelcome and difficult to set up even in communities hit hardest by the epidemic. It is important to understand what metropolitan area characteristics are related to when and if an SEP opens in a particular locality. Logistic regression models are used to explore how need, political factors, SEP diffusion from Tacoma (the first SEP), and metropolitan socioeconomic characteristics are related to SEP presence. Results indicate that need is not a significant predictor of having an SEP. Predictors were the percentage of the population who are men who have sex with men (AOR = 6.95; 95% CI = 1.29-37.49), and metropolitan area population (AOR = 1.08 per 100,000; 95% CI = 1.02-1.14). Predictors of having an SEP in a metropolitan area seem to be political factors and metropolitan area population size, not need among IDUs. Gay political influence and/or support may well facilitate SEP formation, and geographic diffusion may influence where SEPs are established.