This paper introduces a new self-report inventory, the NIMH Panic Questionnaire (NIMH PQ), for obtaining and quantifying comprehensive information about the clinical characteristics of panic disorder in patients with previously diagnosed or suspected illness.Fifty-two patients who met DSM-III-R criteria for panic disorder completed the NIMH PQ; their responses were compared with data derived from 16 similar or identical questions on the Schedule for Affective Disorders and Schizophrenia modified for anxiety disorders. There were no significant differences between the two instruments on 15 of the 16 (93.7%) items tested. The one exception revealed a greater proportion of patients versus physicians endorsing “spontaneous” panic, and a nonsignificant trend for physicians over patients endorsing anticipatory anxiety with greater frequency. The NIMH PQ offers a potentially useful clinical and research tool in the assessment of patients with known or suspected panic disorder.