Within a behavioural framework, staff responses to challenging behaviours have been Identified as likely to ensure the long-term maintenance of such behaviour. However, little has been done to understand why staff behave as they do. The present paper hypothesized that staff's beliefs about the causes of challenging behaviours may be an important factor in determining staff responses to it. Beliefs about causes of three topographies of challenging behaviour (self-injury, stereotypy and aggression) were elicited from 148 experienced and 98 inexperienced institutional staff and nursing students using a questionnaire measure. Results showed that experienced participants held beliefs that were more consistent with contemporary theories of challenging behaviours than inexperienced participants. Experienced participants also distinguished between the behaviours in terms of their causes. These data were interpreted as reflerting a ‘needs-based’ rather than a ‘functional’ approach to intervention for challenging behaviours. Implications for staff training, community living and future research on staff behaviour were briefly considered.