What accounts for low-intensity intergroup violence? In this paper, we explore the micro-level determinants of low-intensity sectarian violence in Northern Ireland, which has marked the post-1998 peace agreement period. We use original cross-sectional time series violence data for the 2005-2012 period at a disaggregated sub-national level, the ward, and a wide variety of social and political indicators. In particular, we assess the impact of within- ward ethnic composition, on the one hand, and the ethnic composition of neighboring wards, on the other. We find that the number of intergroup violent events peak in wards where there is parity between groups, and in predominantly Catholic (Protestant) wards that border predominantly Protestant (Catholic) wards. The rationale is that violence takes place where groups have both opportunities to perpetrate sectarian violence and strategic incentives to do it. The paper makes several contributions: it demonstrates that violence is explained by factors that go beyond underlying enmity between groups; it shows that micro-level dynamics can expand beyond local territorial units; and it suggests that neither ethnic segregation nor peace-walls are likely to prevent intergroup violence.