HIV risk through needle sharing is now an emerging phenomenon in Africa. This article describes the practices that heroin users are producing as they establish the rules and organization surrounding their drug use. Their practices and interactions reveal the ways that they become initiated into its use, how they progress to injecting, and the important role of local neighbourhood hangouts in facilitating this process. Their practices, interactions and narratives also provide insights into what may be the most appropriate HIV-prevention interventions. Semi-structured interviews were conducted during the months of February and July 2003 with 51 male and female injectors residing in 8 neighbourhoods in the Dar es Salaam, Tanzania. Interviews were content coded and codes were collapsed into emergent themes around hangout places, initiation of heroin use, and progression to injecting. Interviews reveal that Dar es Salaam injectors begin smoking heroin in hangout areas with their friends, either because of peer pressure, desire, or trickery. One hangout place in particular, referred to as the 'geto' (ghetto) is the main place where the organization and rules governing heroin use are produced. Three main types of heroin 'ghettoes' are operating in Dar es Salaam. As users build a tolerance for the drug they move along a continuum of practices until they begin to inject. Injecting heroin is a comparatively recent practice in Africa and coincides with: (1) Tanzania transitioning to becoming a heroin consuming community; (2) the growing importance of youth culture; (3) the technical innovation of injecting practices and the introduction and ease of use of white heroin; and (4) heroin smokers, sniffers, and inhalers perceived need to escalate their use through a more effective and satisfying form of heroin ingestion.