The principles at work in psychiatric risk assessment derive from clinical psychiatry, where the results are entered in medical records, communicated verbally or, perhaps most often, used to inform clinical management without ever being articulated. As with clinical assessments, when writing for the courts, the context affects the way in which an opinion is communicated. This chapter discusses risk assessment approaches such as correlation-based approaches, causation-based approaches and structured approaches. Correlation-based approaches assess risk by looking for variables associated with violence. They therefore benefit from the numerous epidemiological data now available describing the relationship between mental disorder and crime. When structured approaches combine those variables into risk assessment instruments they have the additional benefit of allowing the author of a report to make the results transparent. Causation-based approaches work differently. They assume that violence happens for reasons and that clinicians can use their understanding of those reasons to prevent it.