Knowledge is a key element in devising responses to policy problems. In the field of criminal justice policy an obvious problem is the natural desire of the perpetrators of crimes to conceal their activities. This problem of activity identification is compounded in the UK, in the case of organised crime, by the fact that there is no separate organised crime offence category. Therefore organised crime appears neither in recorded crime statistics nor in statistics on convictions. This chapter focuses on the problems of knowledge acquisition, at the official level, on organised crime in the period from 1996-2002. It draws upon hitherto unpublished Home Office sources and locates the raw data gathering process within the context of national, global and regional (EU) crime control agendas. The chapter addresses the topic by examining the general issues related to crime data collection, the origins of the UK’s Organised Crime Notification Scheme (OCNS), the method selected for OCNS data collection, the quantitative and qualitative problems encountered in the management of the OCNS and the problems of evaluating the collected data.