Background: Difficulties identifying anxiety disorders in primary-school aged children present significant barriers to timely access to support and intervention. This study aimed to develop a brief assessment tool that can identify children with anxiety disorders in community settings, with a high level of sensitivity and specificity. Methods: Children (aged 8-11 years), and their parents/carers and teachers from 19 primary/junior schools in England each completed a pool of questionnaire items that assessed child anxiety symptoms and associated impact. Diagnostic assessments (Anxiety Disorder Interview Schedule for Children: Child and Parent interviews) were administered by independent assessors to determine the presence/absence of anxiety disorders in children. We created alternative candidate brief child-, parent-, teacher-report questionnaires consisting of the 'best' items selected from the wider pool of completed items. We used exploratory factor analysis to reduce the item pool, and multivariable backward elimination logistic regression to identify items that were the strongest predictors of the presence/absence of an anxiety disorder. Results: Parents/carers of 646 children provided consent; child/parent/teacher-report questionnaires were collected for 582/646/565 children respectively; and diagnostic outcome data were collected for 463 children. None of the brief child- nor teacher-report questionnaires achieved acceptable sensitivity/specificity (<75%). Parent-report questionnaires including between 2 and 9 items that assess anxiety symptoms and/or associated impact achieved acceptable sensitivity and specificity ([greater than or equal to]75%). Conclusions: The two-item parent-report measure that assesses distress and impairment associated with anxiety brings the advantage of brevity and has the potential to be used in community settings to improve identification of children with anxiety disorders.