If the UN is to effectively monitor compliance with human rights obligations and protect victims from abuse, it is crucial that human rights defenders and victims of human rights violations can access and communicate with the UN freely and safely. A number of States systematically undermine the right to unhindered access to and cooperation with UN human rights mechanisms through intimidation or reprisals. In recent years, the UN has taken some welcome steps to address the issue. However, documenting overt, reported incidents of intimidation and reprisals using standard legalistic case-based methods has been privileged over addressing the kind of intimidation that inhibits defenders from engaging with the UN at all. Perversely, this means very repressive States can escape scrutiny. To begin to tackle this issue, ISHR commissioned a study that considers the methodological challenges and opportunities inherent in measuring the impact of intimidation in particular on engagement with the UN human rights system.