Mental health professionals in forensic settings are increasingly called upon to assess the probability of dangerous behaviour, or level of risk, that certain individuals pose to the community. These assessments may inform decisions concerning the containment and management of violent offenders within forensic settings, sentencing options, and whether or not to grant bail or parole. In this paper we provide an overview of the key issues associated with the assessment of dangerous behaviour. Specifically, we briefly consider the debate on clinical versus actuarial assessments of dangerous behaviour and risk, and provide a synopsis of the current research on dangerous behaviour, focusing on the key areas of mental disorder, psychopathy, and substance use. Finally, we outline guidelines for addressing specific content areas in the clinical risk-assessment process and discuss areas for future research.