This project seeks to expand traumatic stress clinical and research methods by developing and validating an innovative approach to measurement of trauma responses. Ecological Proximal Assessment (EPA) involves collecting self-reports that are frequent and proximal in time to the phenomena of interest by having participants make their reports on hand-held computers (PDAs) in their natural environments. EPA overcomes many limitations of standard measures, and the nature of the data allows use of multilevel data analysis methods to study directionality of relationships and within-person relationships. This project's primary aims are to investigate the feasibility, validity, and utility of EPA for measuring early responses to traumatic events. We will study aspects of recruitment, psychometric validity, and measurement reactivity of EPA in 140 hospital trauma patients or trauma-exposed family members. Using hierarchical linear modeling methods, we will also investigate hypotheses relating to the clinical utility of EPA and the dynamics of posttraumatic moods, cognitions, symptoms, and experiences. Demonstration that EPA is feasible and valid will enable use of the method for clinical assessments and research on between and within-person variables important in the development of posttraumatic psychological disorders. Ultimately, EPA methods may help clinicians identify recent trauma survivors who are at risk for the development of posttraumatic disorders and may allow tailoring of interventions to individual needs.