Although the possibility that a firm's stakeholders may take damaging measures against it in response to its activities has been an underlying assumption of stakeholder theory from inception, the conditions that predispose stakeholders to act against firms remain largely unexplored in the literature. Based on work in equity theory, expectancy theory, and resource dependence theory, we present and test hypotheses concerning stakeholders' propensities to impose sanctions upon-or to supportfirms. Using a vignette-based experiment, we found strong confirmation of the criticality of fairness in the firm-stakeholder relationship: stakeholder equity perceptions were unequivocally associated with the proclivity to sanction the firm, or to engage in prosocial behaviours of benefit to it. Stakeholder expectancy perceptions and resource dependence were related to only certain forms of stakeholder action, indicating that researchers should take care to differentiate between types of stakeholder response when investigating questions surrounding stakeholder mobilization. Our results also suggest specific avenues for stakeholder dialogue that could help firms mitigate the likelihood of stakeholders taking damaging action against them.