This article theorizes about and tests the conditions under which firms' commitment to an industry is influenced by social movement organizations (SMOs) that favor the industry. We argue that the more prominent SMOs are within an industry, the more a firm increases its commitment to that industry by expanding its operations; yet, this main effect should be moderated substantially by a firm's idiosyncratic characteristics. The current research predicts that a firm's location, its sensitivity to information about the industry's potential, and its history of associations with activists determine the magnitude of the effect of SMO prominence on its strategic commitment to the industry. We test and find support for these hypotheses using a longitudinal data set of European manufacturers of solar photovoltaic cells between 1990 and 2011. The findings offer new insights for literature on social movements and organizations, as well as strategic management research. 1 The authors are listed in alphabetical order. We are grateful to Brayden King and three anonymous reviewers for their helpful feedback. We also thank 3 expectations, without investing substantively down the road. Second, research that views social movements as a source of market contentiousness, rather than as market supporters, consistently reports that responses to activism differ depending on the firms' characteristics (King 2008;McDonnell and King 2013;Waldron et al. 2013;Weber et al. 2009). Given these observations, although prior work has documented the macro-level effects of support for new industries by SMOs, the need remains to examine whether SMOs affect concrete investment strategies at the firm level and to understand why firms react differently to SMO prominence.We argue that the more SMOs are prominent in an industry (i.e., the more they are noticed within the industry) the more a firm will increase its commitment to the industry. Because SMO prominence signals shifting general public preferences, reflects active sponsoring of the alternative industry's economic potential, and defines new contours for reputation building, firms will tend to expand their commitment to the alternative industry in this case. Yet we also expect that firms differ in their responses to SMO prominence, particularly because their perceptions of the perceived benefits of social movement support might be magnified or stifled according to the firms' location, prior commitments, or history of associations with activists.Empirically, we focus on the European solar PV (photovoltaics) industry, which has been widely championed by the environmental social movement, -the most comprehensive and influential movement of our times‖ (Castells 1997: 67). To test our hypotheses, we built a longitudinal data set of solar PV cell producers operating in European countries from 1990 to 2011. We operationalize SMO prominence in reference to Greenpeace's presence in the PV industry's professional media and track all producers' production over time. Using growth models and accounting for co...