Contemporary behavioural models of the maintenance of challenging behaviour stress the importance of the behaviour of others in the environment. It is proposed that the interactions between challenging behaviour and caregiver behaviour are mutually reinforcing, and thereby contribute towards the long term maintenance of challenging behaviour . This thesis seeks to build on our current understanding of the processes which influence caregiver behaviour in relation to challenging behaviour. Of the central assumptions of the behavioural systems model (Oliver, 1995), is that challenging behaviour is experienced by others as aversive. The first paper, a literature review, discusses the findings of existing research on caregivers' behavioural and emotional responses to challenging behaviour in relation to this assumption. The second paper seeks to establish the aversive nature of challenging behaviour by demonstrating, using an experimental design, that caregivers experience negative emotions in response to self-injurious behaviour. Also, the effect of the behavioural function of self-injury on emotional reactions is explored. On the basis that some reinforcement processes may be perceived as more controllable than others, it was predicted that there would be differences in emotional reactions to self-injury serving different behavioural functions. Participants were presented with filmed stimuli depicting simulated self-injurious behaviour. The results indicate that participants reported experiencing negative emotional reactions in response to the stimuli. There is some evidence that the behavioural function of the self-injurious behaviour had an effect, although this is not accounted for by attributions of controllability. Clinical and research implications of these findings are discussed.