Although the field of risk assessment has made tremendous advances in the past 20 years, assessments of targeted violence continue to pose a significant challenge to law enforcement, mental health, and other professionals. These specific and critical assessments require an innovative approach. The threat assessment model, developed and refined by the U.S. Secret Service, provides a useful framework for thinking about assessments of potential for targeted violence. In this paper, we attempt to define this approach as it has been developed by the Secret Service, and apply it within the existing professional/scientific literature on risk assessment. We begin with a brief review of existing models and approaches in risk assessment, and identification of some gaps in our existing knowledge as it relates to assessments of targeted violence. We then proceed with an outline of the threat assessment approach, including a review of principles and guiding operational questions, and discussion of its use in assessment of targeted violence.