Background Self-rating scales are widely used in general adult practice; however, there is no reliable and valid method for assessing state anxiety in people with intellectual disability (ID). The present study describes the development and psychometric evaluation of a new scale, the Glasgow Anxiety Scale for People with an Intellectual Disability (GAS-ID). Methods First, an item pool was generated from focus groups, a review of the literature and clinician feedback. Secondly, a draft scale was administered to  anxious and  non-anxious people with ID for further validation and appraisal of reliability. Thirdly, the scale was completed by  anxious, non-ID people for cross-validation with the Beck Anxiety Inventory (BAI). Finally, physiological concomitants were validated by pulse-oximetry. Results The  -item GAS-ID discriminated anxious from non-anxious participants, had good test-retest reliability ( r =  .  ) and internal consistency ( a =  .  ), and was reasonably correlated with the BAI ( r =  .  ). The correlation between the physiological subscale of the GAS-ID and changes in pulse rate was moderately significant ( r =  .  ). Conclusions This preliminary study suggests that the GAS-ID offers a psychometrically robust and practi-

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