Numerous international instruments emphasize that individuals vulnerable to human trafficking need to be better protected (e.g., UN Trafficking Protocol and UNODC Model Law against Trafficking in Persons). Yet, the question that emerges is whether the current substantial body of research provides a solid enough foundation upon which to reliably determine vulnerability of individuals to human trafficking and build effective and evidence-based interventions. Thus, this report focuses on vulnerability to human trafficking and seeks to understand how that vulnerability is being researched, measured, determined, and analyzed.