Injecting drugs in the streets and other public places is increasingly common in many cities and large towns in the United Kingdom. It is a practice rarely open to view, but the evidence is there in the used needles and syringes left in stairwells of flats, shop doorways, public toilets and other areas where exposure can be avoided. Although it is a development with serious implications for public health, it has received little research attention. This paper reports the factors associated with street injecting from 56 polydrug users who regularly injected in public places. It reveals that they were more likely to be severely drug dependent with associated health problems. A high proportion were homeless. Their drug-related and sexual risk behaviour have implications for the acquisition and transmission of disease.