Biopsychosocial consequences of catastrophic events create an ongoing need for research that examines the effects of mass traumas, developing psychosocial interventions, and advocacy to address the needs of affected individuals, systems, and communities. Because it is neither possible nor necessarily desirable to intervene with all touched by disasters at an individual level, a systems approach that allows conceptualization and response at the individual, family, community, and societal levels seems optimal. Many of the models commonly used in counseling psychology to explain coping with difficult events focus on individual effects and do not adequately capture the complex, multisystemic effects of large-scale catastrophic events and disasters. A bioecological model of mass trauma, which provides a conceptual framework for understanding the effects, intervening in the aftermath, addressing prevention, and researching aspects of large-scale disasters, catastrophes, and mass traumas, is presented. Relevant literature and illustrative examples from three categories of mass traumas or catastrophic events (disasters, war, and terrorism or violence) that currently contribute to a persistent atmosphere of stress for many are reviewed using the bioecological model. Recommendations for future research are provided. (Contains 1 figure.)