A 2 [group: high Anxiety Sensitivity Index (ASI), low ASI] X 2 (condition: inhibition, experimental control) mixed model research design will be employed with one, prolonged administration of 10% CO2. Participants will be non-clinical persons selected on the basis of their ASI scores with half scoring one standard deviation above and half below the mean of the standardization sample. Dependent measures will include self-rated anxiety and bodily distress, interpretative biases for threat information, and physiological indices of autonomic arousal. It is expected individuals high in Anxiety Sensitivity (AS) will experience greater negative emotional consequences in the inhibition condition relative to low AS individuals. We also expect response inhibition to increase interpretative biases for threat-related information, particularly within the group high in AS. The proposed study represents the first experimental test of the emotional and cognitive consequences of response inhibition in a panic-relevant paradigm, which holds direct implications for understanding the role of emotion regulation processes in the onset and maintenance of anxious and fearful responding to bodily perturbation.