Aims: This article describes the design of a systematic interdisciplinary clinical tool developed to differentiate levels of challenging behaviour (CB) in patients following a traumatic or acquired brain injury in order to facilitate decisions regarding rehabilitation and management needs. Methods: A 'top-down and bottom-up' approach was used, based on clinical case examples and adaptations from the Overt Aggression Scale - Modifi ed for Neurorehabilitation (OAS-MNR) (Alderman et al, 1997). Inter-rater reliability, face and content validity were tested through opportunistic sampling and blind re-screening of 20 patients on a post-acute neurorehabilitation ward. Findings: Inter-rater reliability for overall decision on suitability for inpatient neurorehabilitation referral was signifi cant (V = 0.84; P = 0.03); with signifi cant inter-rater reliability within CB ratings. Ninety-three percent of staff were able to make an agreed decision regarding overall level of CB; there was a 95% concordance between staff using the tool; 90% of expert neurorehabilitation staff agreed with the decision from the tool, indicating a high degree of feasibility and clinical utility. Conclusions: Changes were made to improve the tool's overall clinical usefulness. Findings indicate it is accessible for ward staff, and appropriate for use as a decision and management aid for patients presenting with a range of CBs. Further exploration of psychometric properties across settings and aetiology of CB is recommended. [ABSTRACT FROM AUTHOR]