This article centres on the hypothesis that human trafficking for sexual exploitation is not only an organised crime activity, but a crime of relational nature as well. Therefore this study explores the relationships that exist between suspects and victims of sex trafficking, and examines to what extent the nature of sex trafficking has parallels with domestic violence. The study is based on an analysis of 12 police investigations into sex trafficking related to window prostitution in the Amsterdam red-light district in the period 2006-2010. The findings suggest that there are intimate relationships between traffickers and victims, and that these relationships display various characteristics of domestic violence. Aside from intimidation, control and violence, factors such as affection and attachment contribute to the persistency of these relationships. This empirical study shows the theoretical and practical importance of focusing on the relational aspects of sex trafficking and the use of domestic violence knowledge to help identify trafficking situations, as well as for the prosecution of cases and to provide assistance to victims. © 2013 Springer Science+Business Media Dordrecht.