People with intellectual disabilities are exposed to a high number of adverse life events, and evidence supports a link between the experience of adverse life events and trauma. Interventions for trauma have been found to be efficacious if case recognition can be facilitated. However to date there are no psychometrically validated measures of trauma for people with intellectual disabilities. This study describes the development of the Lancaster and Northgate Trauma Scales (LANTS), which comprise a self-report and an informant measure of the effects of traumatic life events on people with intellectual disabilities. The pool of items for the measures was created via a systematic review, and consultation with key stakeholders. 99 service users and 88 staff completed the LANTS measures during a pilot. The 29-item self-report LANTS and the 43-item informant LANTS were found to have good psychometric properties, including internal and test retest reliability, plus convergent and construct validity. The findings suggest the LANTS are promising trauma screening tools for use in clinical and research settings.