Behavioural assessment methods have been used to signal the need for intervention and to evaluate treatment effectiveness. Direct observation and rating scales have been used to assess pain and distress associated with acute medical procedures, postoperative pain, critical care, analogue pain induction procedures and other sources. Two recent scholarly reviews of behavioural assessment methods were conducted by the Society of Pediatric Psychology Evidence-Based Assessment Task Force and the Pediatric Initiative on Methods, Measurement, and Pain Assessment in Clinical Trials, which classified various instruments as well established, approaching well established or promising. The characteristics of the eight behavioural assessment scales that were recommended by one of these task forces are further reviewed in the present paper. The results indicate that behavioural assessment scales have been used flexibly to assess pain in a wide variety of situations, across different pediatric populations and for patients of different ages. In the present review, there appears to be no basis for designating the scales as measures of distress versus pain; both emotional and sensory components of pain seem to be assessed by each of the scales. There is considerable overlap among the behavioural indicators of pain used in the different scales. Furthermore, the behavioural codes indicative of pain may occur before, during and after painful events. Recommendations for future research are provided, including using behavioural assessment to focus on children’s coping and adults’ behaviours, as well as pain.