This historical monograph addresses a gap in the extensive scholarly research literature devoted to comparative advertising—especially that which contrasts the advertised product, service, or brand with an identifiable competitor—by exploring advertisers’ explanations for its appeal as a tactic throughout the previous century. Prior historical research confirms advertisers have long been aware of and greatly concerned about the unintended consequences of what they often called excessively competitive and combative advertising. Moreover, despite some thirty-five years of systematic scholarly research, two research teams recently concluded that the state of empirical knowledge regarding its effectiveness remains “equivocal.” By synthesizing the extensive theoretical and empirical research literature on comparative advertising and interpreting those findings from a historical perspective, this monograph offers uniquely significant insights into modern advertising’s history, theory, and practice.