Discomfort intolerance, defined as an individual difference in the capacity to tolerate unpleasant bodily sensations, is a construct recently posited as a risk factor for panic and anxiety psychopathology. The present report used a biological challenge procedure to evaluate whether discomfort intolerance predicts fearful responding beyond the effects of trait anxiety and a well-established psychological vulnerability factor (i.e., anxiety sensitivity). Nonclinical community participants (N=44) with no history of panic attacks or any Axis I condition completed a 35% CO(2) challenge. Results are consistent with our hypothesis suggesting that discomfort intolerance incrementally predicts increased subjective reactivity to the challenge. Moreover, there was some suggestion that discomfort intolerance interacted synergistically with anxiety sensitivity to increase anxiety-related symptoms. These findings add to a small but growing literature suggesting that discomfort intolerance may play a role in the development of anxiety problems.