The content and psychometric properties of the Claustrophobia Questionnaire (CLQ) are described. An earlier version of the CLQ was developed to test the hypothesis that claustrophobia is comprised of two distinct but related fears--the fear of suffocation and the fear of restriction [J. Anxiety Disord. 7 (1993) 281.]. The scale was used to assess patients undergoing the magnetic resonance imaging (MRI) procedure [J. Behav. Med. 21 (1998) 255.] and in participants with panic disorder [J. Abnorm. Psychol. 105 (1996) 146; Taylor, S., Rachman, S., & Radomsky, A. S. (1996). The prediction of panic: a comparison of suffocation false alarm and cognitive theories. Unpublished data.]. On the basis of these studies, we decided to revise and shorten the CLQ, collect normative data, and provide information on the scale's predictive and discriminant validity as well as its internal consistency and test-retest reliability. This was done through a set of four interconnected studies that included psychometric analyses of undergraduate and community adult questionnaire responses and behavioural testing. Results indicate that the CLQ has good predictive and discriminant validity as well as good internal consistency and test-retest reliability. The CLQ appears to be a reliable and sensitive measure of claustrophobia and its component fears. We encourage the use of the CLQ in a variety of clinical and research applications. The scale is provided in this paper for public use.