This article analyzes how a new social movement against genetic engineering in agriculture managed to turn a major industry upside down. While the social movements literature has long recognized the importance of external context for the success of social movements, it has paid little attention to the institutional logic and features of targets other than the state. Here I argue that an undertheorized aspect of external context, namely, industry structures, is a primary factor explaining why the anti-biotech movement in Western Europe was so effective. As conceptualized here, industry structures are composed of economic, organizational, and cultural features, and function to enhance or constrain social movements' efforts to change industry behavior. Bringing these structures into our purview and recognizing their significance for activist struggles can significantly advance our understanding of social movement efficacy in this age of globalization and increased corporate power.