This report is the main outcome of a study commissioned by Knowledge Exchange (KE). The study was aimed at investigating “Risks and trust in pursuit of a well functioning Persistent Identifier infrastructure for research”. The investigation set out to analyse the current state of the Persistent Identifier (PID) landscape in the six Knowledge Exchange partner countries and beyond, taking emerging PIDs particularly into account and examining the roles of relevant stakeholders as PID service providers, higher education institutions, researchers, publishers and national libraries. The report examines the PID landscape and provides a detailed look at what can go wrong with an unreliable PID service. In addition, a series of recommendations aimed at each stakeholder group are presented. Seven complementary case studies accompany the report, helping provide a deeper insight into specific areas of activity, workflows and stakeholders within this wider PID landscape. Each can be accessed through the report.