Human trafficking is a humanitarian problem of global scale, but quantitative research on the issue barely exists. This paper is the first attempt to analyze the economics of human trafficking and labour migration based on micro data, using unique household surveys from Belarus, Bulgaria, Moldova, Romania, and Ukraine. The main result is that individual trafficking risks are much higher in regions with large emigration flows. The reasons are lower recruitment costs for traffickers in emigration areas and, to a lesser extent, negative self-selection into migration. Our results also indicate that illegal migration increases trafficking risks and that better information, e.g. through awareness campaigns, might be an effective strategy to reduce the crime. These findings may help policymakers to better target anti-trafficking efforts.