This paper deals with the question why rebels groups in intrastate conflicts choose to kill civilians, despite both domestic and international audience costs. From a bargaining perspective, I argue that rebels that are losing on the battlefield may target civilians in order to signal their resolve to the government. Since it is assumed to be a costly action, the rebels can thereby prove their determination to continue and consequently affect the overall bargaining range of the conflict. A further implication of the argument is that conflict duration should have negative effects on rebel violence against civilians, since the expected effect of violence as a signal decreases over time. The study is based on a dataset with monthly observations over rebel killings of civilians in all intrastate armed conflicts from January 2002 to December 2004. The hypotheses are tested using a zero-inflated negative binomial regression model, and the empirical results support the theoretical argument.