Americans have been exposed to increased levels of mass violence during the past decade. School violence, shootings in the workplace, and terrorist acts both here and abroad--all have affected individuals, families, communities, and our country. This report addresses the urgent need to evaluate the various psychological interventions that are increasingly among the first responses to these traumatic events. At a workshop held from October 30 to November 1, 2001, 58 disaster mental health experts from six countries were invited to address the impact of early psychological interventions and to identify what works, what doesn't work, and what the gaps are in our knowledge. Prior to the workshop, leading mental health research clinicians from the United States, Australia, and the United Kingdom prepared a review of the published, peer-reviewed literature (tables appear in Appendix G and references appear in Appendix I). Workshop participants examined research on critical issues related to the following questions: What early interventions can be recommended in mass violence situations? What should the key operating principles be? What are the issues of timing of early intervention? What is appropriate screening? What is appropriate follow-up, for whom, over what period of time? What expertise, skills, and training are necessary for early interventions, at what level of sophistication? What is the role of research and evaluation? What are the ethical issues involved in early interventions? What are the key questions for the field of early intervention that have not yet been thoroughly researched?