This chapter in Miradas críticas de la trata de seres humanos: Un dialogo académico en construcción (Critical views on human trafficking: an academic dialogue in construction) considers success measurements with respect to anti-trafficking criminal justice interventions. The authors (Anne Gallagher and Rebecca Surtees) seek to cut through the complexities presented by multiple theories and elaborate methodologies by focusing on one key issue: who decides success, and how? Their review of evaluation reports and interviews with practitioners confirms that determinations of success (or failure) will vary according to: (i) whom one consults and their role in the intervention; (ii) the criteria against which success is measured; and (iii) the assumptions that are built into that criteria. Each aspect is considered with reference to examples and insights drawn from recent practice. A major finding of the chapter is that the lack of an overarching vision of what “success” might look like allows mediocre or even harmful interventions to flourish and good work to go unrecognized and unrewarded. Global concern about human trafficking has prompted substantial investment in counter-trafficking interventions. That investment, and the human rights imperatives that underpin counter-trafficking work, demand that interventions demonstrate accountability, results and beneficial impact. The chapter is in Spanish.