The PAS is the first ever scale for assessing the severity of panic disorder with or without agoraphobia. Compatible with both DSM-IV and ICD-10 classifications, and available in both self-related and observer-related versions, the PAS was specially developed for monitoring the efficacy of both drug and psychotherapy treatments. In addition to the English scale, translations are available in Arabic, Danish, Dutch, French, German, Greek, Hebrew, Hungarian, Italian, Japanese, Portuguese, Serbocroat, Spanish, Swedish, and Turkish. The PAS has excellent psychometric properties, and is quick to use (the observer-rated version can be completed in 5-10 minutes). It has been successfully applied in both double-blind placebo-controlled studies and open treatment trials, and can be used by clinicians as well as for research purposes. This manual describes the development of the scale, shows how to use it and evaluates results, and details its psychometric properties. In addition, both the self-related and the observer-rated versions in all 17 different languages are reproduced.