This chapter summarizes and synthesizes the existing scientific research and recent professional literature that is most directly relevant to risk assessment practice in the context of violent extremism. It is written mainly for practitioners. It starts with a set of consensus points and assumptions on terrorism risk assessment developed in 2017 by a multidisciplinary, international group of practitioners and academics, all with expertise in risk assessment and violent extremism. It reviews the concept of evidence-based risk assessment as it applies to violent extremism. Then, it discusses various risk outcomes (e.g., types of violent extremism, phases of involvement, and ways to be involved) and relevant risk and protective factors and how to apply those in VE-related risk assessments. It concludes the evolution of risk assessment approaches and the ascendance of Structured Professional Judgement (SPJ) as a best practice model.