The present study describes the development of a short, general measure of experiential avoidance, based on a specific theoretical approach to this process. A theoretically driven iterative exploratory analysis using structural equation modeling on data from a clinical sample yielded a single factor comprising 9 items. A fully confirmatory factor analysis upheld this same 9-item factor in an independent clinical sample. The operational characteristics of the Acceptance and Action Questionnaire (AAQ) were then examined in 8 additional samples. All totaled, over 2,400 participants were studied. As expected, higher levels of experiential avoidance were associated with higher levels of general psychopathology, depression, anxiety, a variety of specific fears, trauma, and a lower quality of life. The AAQ related to more specific measures of avoidant coping and to self-deceptive positivity, but the relation to psychopathology could not be fully accounted for by these alternative measures. The data provide some initial support for the model of experiential avoidance based on Relational Frame Theory that is incorporated into Acceptance and Commitment Therapy, and provides researchers with a preliminary measure for use in population-based studies on experiential avoidance.