Despite the plethora of rating scales for anxiety disorders and agoraphobia, a qualified scale for assessing the severity of panic disorder and agoraphobia (PDA) is still lacking. The new Panic and Agoraphobia Scale (P&A) is presented in this paper. It was developed to assess the degree of severity of these disorders after a diagnosis has been made according to the criteria of the DSM-III-R/IV or the ICD-10. The P&A was specially developed for use in clinical drug trials. Factors which impair the quality of life in panic disorder and agoraphobia patients (panic attacks, phobic avoidance, anticipatory anxiety, impairment in social relationships and work, assumption of somatic disease) were considered in the development of this scale so that the efficacy of a certain drug therapy on each of these factors can be assessed separately. Both an observer rating and a self-rating with matching items are available. The observer rating only takes about 10 minutes to complete. Translation into many European languages is planned so that it can be used in multicentre trials. Satisfactory results of item analysis, inter-rater reliability, objectivity, external validity and factor structure are presented. The P&A should be a useful tool for assessing the severity of PDA and may solve some of the methodological problems that have arisen in former PDA studies.