This is the first of two articles empirically detailing the working practices of regulators who are charged with overseeing biological research. Specifically, it considers how regulators from the Biological Agents Unit of the UK Health and Safety Executive review notifications and applications, carry out inspections of research centres, and enforce the law once breaches are uncovered. This first article focuses on the Unit's working practices before 9/11, and the second, forthcoming article focuses on the Unit's working practices after 9/11. I argue that an understanding of the implementation processes--that is, the strategies adopted by regulatory agencies and the styles employed by agency regulators in their interactions with those regulated--is critical to developing a coherent policy logic for the developing regulatory regime around biorisks.