The focus is on the nature of human trafficking and how it is being investigated in the Amsterdam red light district. This involved determining how victims are exploited; the characteristics of victims and suspects involved in human trafficking; the choices made in criminal investigations of human trafficking in the red light district; and whether it is possible to distinguish factors that can either advance or impede such criminal investigations. The findings are based on criminal files of 12 investigations into human trafficking in the Amsterdam red light district. They were conducted by the police in the period between 2006 and 2010. Face-to-face interviews were conducted with the police team leaders in charge of the investigations. In two recent investigations, the researchers were allowed to accompany the detectives for the duration of the investigations. The study focused on four dimensions of the investigations: duration (brief or long-term); its scope (local or international); the exchange of information with other investigative partners before, during, or as the result of a criminal investigation (a lot or little exchange of information); and the focus of the investigation (the victim or the suspected offender). The investigative guidelines, opportunities, and choices within these four dimensions are examined. 74 references