This dissertation inductively conceptualizes how activist organizations engage in nontraditional rivalry with firms. Using cluster and qualitative analysis of 778 such attacks as an inferential base, I identify three distinct activist attack strategies (political, public, and private pressure); explain the disruptive effects of these strategies on corporate resources; and proposeactivist legitimacy, experience, and organizational coupling shape the use of these strategies. These concepts and propositions represent a conceptual framework that informs research on inter-organizational competition and offers implications for practice.