The present investigation applied Item Response Theory (IRT) methodology to the 16-item Anxiety Sensitivity Index (ASI) [Reiss, S., Peterson, R. A., Gursky, M., & McNally, R. J. (1986). Anxiety sensitivity, anxiety frequency, and the prediction of fearfulness. Behaviour Research and Therapy, 24, 1-8] for a sample of 475 daily adult smokers (52% women; M(age)=26.9, S.D.=11.1, range=18-65). Using non-parametric item response analysis, all 16 ASI items were evaluated. Evaluation of the option characteristic curves for each item revealed 4 poorly discriminating ASI items (1: "It is important not to appear nervous;" 5: "It is important to me to stay in control of my emotions;" 7: "It embarrasses me when my stomach growls;" 9: "When I notice my heart beating rapidly, I worry that I might be having a heart attack"), which were dropped from analysis. Upon repeat analysis, the remaining items appeared to make adequate separations within levels of anxiety sensitivity in this sample. Graded response modeling data indicated important differences in ASI items' capacity to discriminate between, and provide information about, latent levels of anxiety sensitivity. Specifically, three items best discriminated and provided the most information regarding latent levels of AS-items 3, 15, and 16. Items 1, 5, 7, and 9 were omitted due to their limited capacity to discriminate between latent levels of anxiety sensitivity; items 8, 12, and 13 also performed poorly. Overall, current findings suggest that evaluation of anxiety sensitivity among adult smokers using the 16-item ASI may usefully choose to focus on items that performed well in these IRT analyses (items: 2, 3, 4, 6, 10, 11, 14, 15, and 16).