To date, primary research in the area of panic disorder and similar anxiety pathology has been laboratory-based. A wealth of primary research in panic disorder in particular has been gleaned from laboratory research using biological challenge paradigms by which panic is experimentally provoked. The present work reviews the knowledge based gleaned from the biological challenge paradigm and the competing (and often agreeing) models of panic and anxiety, narrowing to a focus on expectancy theory. Within expectancy theory, emphasis is placed upon the role of anxiety sensitivity. Expectancy theory proposes that anxiety sensitivity may serve as a premorbid risk factor for the development of anxiety pathology . Next, this work presents a series of five reports investigating the role of anxiety sensitivity and psychological vulnerability in a number of areas. In addition, the concept of psychological vulnerability factors in general is explored, and other possible risk factors for anxiety pathology, depression, disability, and impairment are examined. The first three reports presented here stem from a large sample of data collected at the U.S. Air Force Academy (USAFA) during Basic Cadet Training (BCT) in the summer of 1995.The remaining two studies examine the theoretical position of anxiety sensitivity in terms iv of pathology specificity and other more distal effects of elevated anxiety sensitivity such as decreased cardiovascular fitness (Schmidt, Lerew, Santiago, Trakowski, & Staab, under review).The current studies are discussed in terms of the practical implications of findings regarding anxiety sensitivity, the relationship between vulnerability and impairment, and other potential vulnerability factors. In addition, the status of expectancy theory ) is discussed as a whole and comments are made concerning the ongoing debate regarding anxiety sensitivity and its relationship to trait anxiety. Data suggest that primary prevention of anxiety pathology may be possible with a focus on malleable vulnerability factors. and Procedure ........................................................................................................75 Measures Participants and Procedure ......................................................................................................125 Measures .................................................................................................................................. 195 Other Sensitivities......................................................................................................................197 The Specificity of Anxiety Sensitivity ........................................................................................199 ANXIETY Anxiety is an innate, adaptive mechanism that readies human beings for action and protects them from anticipated threat. Unfortunately, this alarm system can become maladaptive when it is triggered for excessive lengths of time, triggered in situations known to be harmless, or when it is triggered for no appa...