The Paediatric Pain Profile (PPP) is a 20-item behavior-rating scale designed to assess pain in children with severe to profound neurological impairment. Three raters independently used the PPP to rate behavior of 29 children (mean age 9.6, SD 5.8) filmed during everyday morning activities. The validation process included assessment of interrater reliability and exploration of the relationship of PPP scores with saliva cortisol concentration. There was substantial agreement between raters. The PPP showed strong association with global pain assessments and differentiated between preselected high- and low-pain groups. PPP score showed moderate correlation with saliva cortisol concentration, but a single child explained the strength of the relationship and overall, saliva cortisol concentrations appeared low. The data provide additional evidence that the PPP is a reliable and valid instrument for pain assessment in neurologically impaired children. Cortisol levels are not a useful criterion for pain in this population and further study of cortisol response to stress/pain in children with severe neurological impairments is needed.