Anxiety sensitivity is the fear of anxiety-related sensations, and is measured by the 16-item Anxiety Sensitivity Index (ASI). Despite the popularity and utility of the ASI in research, a number of studies have provided evidence for the inadequacy of several items, and item-to-scale correlations for the ASI have not been published. In this study, a converging set of analyses to evaluate the item adequacy and factor structure of the ASI was used. The results of these multiple analyses converged nicely suggesting that Items 1, 5, 7, 8, and 13 should be considered for removal from the instrument. The impact of removing these problematic items from the scale was explored through the reanalysis of data from 3 previously published studies that compared the original ASI with the new 11-item version (the ASI minus the 5 problematic items). The results of these analyses suggest that the 2 scales function comparably in many respects but that the new version may be a more precise measure of anxiety sensitivity. The 11-item ASI appears to tap 2 primary aspects of anxiety sensitivity: fears of somatic sensations of anxiety and fears of loss of mental control. Suggestions for further development of the ASI are offered.