This thesis considers theories about the relationship between theatre makers and audience members in theatre – how this relationship is established and how it can break down. The thesis posits that the breakdown of a theatre relationship is manifested in audience behaviour which, when it is severe enough, can lead to interventions in performance and, potentially, the breakdown of that performance. The thesis argues that audience intervention in a performance constitutes a seizure of ‘performance power’ from the theatre makers, which is sufficiently difficult to achieve that successful and sustained interventions can only be carried out by groups of audience members and, probably, organized in advance. Further, the thesis suggests that in its most extreme form, such interventions may bring about a transfer of roles and power between audience members and theatre makers such that a new quasi-theatrical ‘performance of protest’ is created. The thesis surveys three historical cases in which theatre performances were disrupted by deliberate audience interventions. In each case the nature of the intervention was slightly different and the effect upon the performance was also different. In the first example, the Plough and the Stars riots (Dublin, 1926) a preplanned protest occurred in the playhouse and, despite interruption, the performance continued. In the second instance, the audience at Living Theatre’s Paradise Now (California 1969) erupted in spontaneous protest within the theatre and the performance was almost entirely subsumed. In the final study, the Mervyn Thompson case (Auckland 1984) the protest took two forms: first there was a vigilante-style attack on Thompson himself which took place well away from any theatre event but had strong theatrical references; then several of his performances were affected by organized lobbying, pickets and interruptions. The thesis asks why the rupture in the theatre relationship occurred in each case and considers what these instances have to tell us about the breakdown of theatre performance as a social phenomenon. The thesis finds that in all three cases the audience members carrying out the interventions belonged to pre-existing groups with prior experience in protest action. The thesis also finds that the protesters had all had direct experience of some other ‘dramatic’ or ‘theatrical’ event in their own lives; experiences that made the performance seem less relevant. Given this, the thesis argues that, in these cases, the propensity to disrupt was brought to the theatre relationship by the audience members rather than being a direct response to the performance, even where that performance was confrontational. These findings have implications for theatre study and practice: in particular, the thesis raises questions about how we look at performance breakdown. Rather than assuming audience protest is a simple response to the performance, the findings suggest that such events must be considered in the light of the wider social and political context of the performance, most particularly the audience members’ pre-occupations. Finally, the thesis asks whether audience protest, however theatrical it appears, can ever become substitute theatre in the true sense of that word.