Fear of arousal symptoms, often referred to as anxiety sensitivity (AS), appears to be associated with risk for anxiety pathology and other Axis I conditions. However, AS is only one of three fundamental components of Reiss' Expectancy Model proposed to account for the development of anxiety problems. Very little research has focused on the other two components of this model (Fear of Negative Evaluation, Illness/Injury Sensitivity) and the specificity of AS, relative to these other two components, has rarely been evaluated. This study evaluated general and unique associations among all three so-called fundamental sensitivities to fearful responding to a biological challenge in a nonclinical sample (N=404). Participants were administered a 20-s inhalation of 20% CO2/balance O2. Consistent with hypothesis, only AS uniquely contributed to increased subjective fear responding to the challenge. These findings are consistent with Expectancy Theory in suggesting that the AS component of the model is specific to amplification of fears to arousal cues.