Unlike in more established professions, there was rarely a pre-existing set of guidelines which HIV prevention outreach workers agreed to abide by as a condition of their employment. More usually, they were involved in a process of boundary creation and development. This meant that alongside any organisational rules, workers developed their own ideas about where and how boundaries should be made. A major feature of this chapter is its emphasis on boundary making as something that is both intuitive and learned. Through a discussion of how workers used a distinction between ‘clients’ and ‘contacts’ to help guide their behaviour, it is shown how boundary making also relied on pre-existing ideas about vulnerability, trust and power relationships.