To create a checklist of behaviours that caregivers could use to determine pain in non-verbal individuals with mental retardation, primary caregivers were recruited by the Division of Neurology and interviewed using a semistructured interview. Caregivers of 20 individuals were asked to recall two instances of short, sharp pain and two of longer-lasting pain and describe the individual's behaviour. Transcribed interviews were reviewed by two of the authors and sets of non-overlapping items were developed. Average age of the 20 individuals was 14.5 years (range 6 to 29 years) and language level averaged 10 months as scored by the MacArthur Communicative Development Inventory. All had mental retardation and 18 had epilepsy and spastic quadriplegia or hemiparesis. Thirty-one behaviours were extracted from the interviews. The specific behaviours were often different from one child to another but the classes of behaviours (Vocal, Eating/Sleeping, Social/Personality, Facial expression of pain, Activity, Body and limbs, and Physiological) were common to almost all children. Reliability of using the checklist on interviews was very good (kappa=0.77). The checklist has excellent content validity and will be useful for caregivers of cognitively-impaired, non-verbal individuals to report on pain behaviours. Further research is needed to additionally assess its validity and sensitivity.