Because of their physical and general health problems, people with a combination of profound intellectual and severe or profound motor disabilities (PIMD) are at risk of pain-related medical conditions. They are fully dependent on support professionals for the detection and accurate interpretation of nonverbal pain behaviour. These professionals can use a recently developed instrument, the Pain Behaviour Checklist (PBC), to assess pain in post-operative situations for children with PIMD. It is not yet known whether this instrument can also be used to identify pain in both children and adults in daily care situations. The aim of this pilot study was therefore threefold: to establish (1) whether the PBC can be used to identify pain in day-to-day situations in people with PIMD, (2) which behaviours are most frequently identified as indices of pain behaviour, and (3) whether there is a difference in pain-related behaviour between children and adults. In total, 32 people with PIMD participated in the study (16 children with a mean age of 10.4 years and 16 adults with a mean age of 46.7 years). Each participant was videotaped twice during a planned care moment in which we assumed that pain was prevalent. During each observation, pain was scored by the direct support professional using the Visual Analogue Scale (VAS) and by two trained independent observers using the PBC. The reliability (both intrarater and interrater) of the PBC was analysed by calculating Spearman's rho. Validity was analysed by correlating the PBC with the VAS scores; Phi was calculated for both children and adults. Finally, positive scores on each separate item of the PBC were analysed in adults and children in order to discover possible differences between pain behaviour in each group. The interrater reliability of the PBC is 0.63 (p less than 0.05) and the intrarater reliability was 0.88 (p less than 0.05). Phi, as a measure of the agreement on pain/no pain between the VAS and the PBC, is 0.75 (p less than 0.05) in children and 0.28 (p less than 0.05) in adults. Adults were more likely to exhibit the pain-related behaviours of "tense face", "deeper naso-labial furrow" and "moaning and groaning", whereas children made more "penetrating sounds of restlessness". Based on this pilot study, we conclude that the PCB's reliability when used in daily practice with people with PIMD is satisfactory. However, although the validity is good for children, it appears insufficient for adults. It seems that children display different pain-related behaviours than adults. More research is needed into the proper assessment of pain in people with PIMD, especially adults, by health care professionals in daily practice. We also need a better understanding of the extent to which the knowledge and experience of care professionals play a role in detecting (chronic) pain behaviour in both children and adults and of how people with PIMD cope with pain. (Contains 2 tables and 2 figures.)