<h3>ABSTRACT</h3> Media activities generated by consumers or communities that are neither paid for nor induced by brand owners are claimed to have a potentially game-changing impact on communication and brand building. In this study, the authors propose a rigorous methodology to assess the impact of this type of social media activities on the actual performance of brands in the market. The article begins by developing a four-step process to condense the complex reality of micro-social-media events for a brand into a manageable set of social media indicators (SMI). These SMI subsequently are used as a subset of the drivers, together with more traditional marketing-mix elements—in a general market-response model—to estimate their relative impact on brand performance in the market. This methodology is illustrated with two real-world examples—one in the market for flat-screen-television market and the other in the set of Internet broadband-service providers.