The development of a 21-item self-report inventory for measuring the severity of anxiety in psychiatric populations is described. The initial item pool of 86 items were drawn from three preexisting scales: the Anxiety Checklist, the Physician's Desk Reference Checklist, and the Situational Anxiety Checklist. A series of analyses was usd to reduce the item pool. The resulting Beck Anxiety Inventory (BAI) is a 21-item scale that showed high internal consistency (α=. 92) and test–retest reliability over 1 week, r (81)=. 75. The BAI discriminated anxious diagnostic groups (panic disorder, generalized anxiety disorder, etc.) from nonanxious diagnostic groups (major depression, dysthymic disorder, etc.). In addition, the BAI was moderately correlated with the revised Hamilton Anxiety Rating Scale, r (150)=. 51, and was only mildly correlated with the revised Hamilton Depression Rating Scale, r (153)=. 25.(PsycInfo Database Record (c) 2022 APA, all rights reserved)