This paper provides a socio-spatial analysis of injecting drug-use in public space. It focuses on one urban district in Melbourne, Australia, which has become strongly identified with heroin sale and use in public space. Selling activities are camouflaged within a diverse street life while injecting sites are dispersed through a broad diversity of laneways, car parks and toilets. These injecting zones occupy liminal places which slide between categories of private and public, and which mediate complex and paradoxical relations between safety and danger. Those who inject in public space are caught in a dilemma--needing both privacy and exposure in the event of an overdose, safety from police becomes danger from an overdose. This empirical work, based on interview and spatial analysis, is presented as a basis for theorizing the socio-spatial construction of heroin use and for assessing the prospects for safe injecting.