In this paper we investigate the effect of search engine brand (i.e., identifying name that distinguishes a product from its competitors) on evaluation of system performance. Our research is motivated by the large amount of search traffic directed to less than a handful of Web search engines, even though many are of equal technical quality with similar interfaces. We conducted a laboratory experiment with 32 participants measuring the effect of four search engine brands while controlling for the quality of search engine results. Based on average relevance ratings, there was a 25% difference between the most highly rated search engine and the lowest, even though search engine results were identical in both content and presentation. We discuss implications for search engine marketing and the design of empirical studies measuring search engine quality.