PROBLEM: Clinicians and researchers require a valid way to assess procedural pain experienced by infants and children. The Modified Behavioral Pain Scale (MBPS) has been used to assess immunisation pain. However, it is unknown whether it is valid for this purpose and whether use can be extended to other procedures. The aim of this study was to rigorously assess evidence addressing the psychometric properties of this scale and to provide recommendations for its use. ELIGIBILITY CRITERIA: Psychometric evaluation studies reporting feasibility, reliability, validity, or utility data for the MBPS applied to children (birth to 18years) and randomised controlled trials (RCT) using the MBPS were included. SAMPLE: Twenty-eight studies (8 psychometric and 20 RCTs) were included. RESULTS: Studies were of varying quality. Sufficient data was available to cautiously accept the MBPS as valid for assessing immunisation related pain in infants aged 2 to 22months. There was insufficient data to support the psychometrics in other age groups or in circumstances other than immunisation. There is no data addressing the clinical utility of the MBPS. CONCLUSIONS: It is not possible at this time to confidently accept the MBPS as suitable for assessing all procedural pain in young children. IMPLICATIONS: Studies to evaluate the capacity of the MBPS to assess pain in a range of procedures and to distinguish between pain and non-pain related distress are needed if it is to be recommended.