This article bridges two important subjects in strategy: competitor analysis and interfirm rivalry. Through a refined conceptualization of competitor analysis, the article introduces two firm-specific, theory-based constructs: market commonality, developed from the literature on multiple-point competition, and resource similarity, derived from the resource-based theory of the firm. The joint consideration of these two constructs shows the complementarity of these two prominent but contrasting strategy theories. Each firm has a unique market profile and strategic resource endowment, and a pair-wise comparison with a given competitor along these two dimensions will help to illuminate the prebattle competitive tension between these two firms and to predict how a focal firm may interact with each of its competitors. The idea of competitive asymmetry is introduced, that is, the notion that a given pair of firms may not pose an equal degree of threat to each other. To illustrate competitor mapping, measures of these two constructs are proposed, and an example is offered. The article ends with a number of implications for research and practice.