Leveraging suppliers resources and capabilities via category management has become the focus of widespread attention in the supermarket industry, as retailers seek competitive advantage in the face of industry consolidation, globalization, and the rapid expansion of mass merchandisers into the grocery market (ACNielsen 1998; Gruen and Shah 2000; Hopkins 2003). Category management concerns treating sets of complementary and/or competing brands in retail settings as strategic business units and allocating resources within these categories to maximize planned outcomes (e.g., Blattberg and Fox 1995; Dhar, Hoch, and Kumar 2001; Zenor 1994). Category management therefore involves the analysis of category-level data, setting goals for category performance, and the formulation and execution of category plans, all of which might be undertaken with varying degrees of involvement from suppliers (Basuroy, Mantrala, and Walters 2001; Dussart 1998). However, analysts suggest that retailers can enjoy significant performance benefits if retailers allow a focal supplier to assume the role of "category captain" where the supplier undertakes or has significant input into the retailer's category management (e.g., Blattberg and Fox 1995; Cannondale 1999; Freedman, Reyner, and Tochtermann 1997). Despite this, fear and/or experience of supplier opportunism means that many retailers are either unconvinced or report having failed to make such category management relationships with focal suppliers work (e.g., Brandweek 1999; Supermarket Business 1999). The literature offers surprisingly little guidance to retailer and supplier managers regarding this important issue. There has been little empirical study of category management generally, and no research focused on the key issue of focal supplier opportunism at the category level (Dhar et al. 2001; Gruen and Shah 2000). The literature reveals a number of different theories relevant to understanding buyer-supplier relationships (e.g., transaction cost analysis, relational exchange, resource dependence, etc.) and their impact on firm performance (resource- based view, industrial organization, etc.). However, many of these theories offer different viewpoints on various aspects of supplier-retailer relationships in category management, and none provide a comprehensive framework that permits the broad understanding of this complex issue required by retailers. For example, most theory and empirical evidence regarding buyer-seller relationships adopts a dyadic perspective, either focusing on a single buyer-supplier relationship (e.g., Dyer and Singh 1998; Jap 1999), or treating each supplier relationship with a common buyer separately (e.g., Subramani and Venkatraman 2003). Yet, since retailers have more than one supplier to almost all categories, and prescriptions advocate giving a key supplier significant influence over retailer category management, the retailer-focal supplier relationship may affect relationships with other suppliers to the category in ways that impact the retailer performance. Since these conditions have not been addressed in previous theory development and empirical research, the literature has little guidance to offer managers facing such situations. This research contributes to theories of interfirm relations and competitive advantage and offers guidance for retailer and supplier managers by developing and testing a model of opportunism among focal suppliers at the category-level, its antecedents, and associated performance outcomes. Our research contributes to knowledge in three areas.… [ABSTRACT FROM AUTHOR]