This study investigates the relationship between a heroin dealer, his customers, and resulting HIV risk behaviors within the context of a multi-level heroin-dealing network. Since the advent of HIV, a primary emphasis of applied drug research has been understanding individual drug injector's risk behavior. Injection behaviors have been qualitatively described, quantified, and innovative intervention models have been developed to address HIV risks. Less attention has been devoted to research on the environmental, political, and economic contexts in which users live and consume drugs. This proposal addresses the disjunction between these topics. Using ethnographic methods within a case study framework, this research will examine the organizational structure and business operation of a multi-level heroin-dealing network in Denver, Colorado. In addition to understanding how the illicit drug market works, the findings of this research will examine the influence of heroin dealing on HIV injection risk behaviors within asymmetric power relations inherent in a multi-level heroin dealing network. Specifically, the aims of this proposal are twofold: One, to understand and document economic and social exchange between heroin dealers and their customers (i.e. users), within a multi- level heroin-dealing network. And two, to investigate the drug injection behaviors and HIV risk which result from heroin dealing activities and transactions.