The Childhood Anxiety Sensitivity Index (CASI) is an 18-item self-report tool designed to measure the construct of anxiety sensitivity (i.e. the belief that anxiety may have harmful consequences such as sickness, embarrassment, or loss of control) in children and adolescents. Previous factor analytic examinations of the CASI have produced varied results. Gender may play a role in this observed variability. In an effort to confirm the factor structure of the measure across gender, CASI items for 671 children and adolescents were subjected to confirmatory factor analysis. Results indicated that for boys two-, three-, and four-factor structures provided a relatively good fit to the data, with the three-factor structure emerging as having the best fit overall. In contrast, for girls only the three-factor structure fitted the data well. Direct comparison of fit of the three-factor model across gender provided evidence to support the notion that childhood anxiety sensitivity is similar in structure across gender.