Despite the value of Williamson's (1975; transaction cost economics perspective to organization theorists for offering new ways of thinking about relations between organizations, its focus on supplierbuyer dyads operating on a continuum ranging from markets to hierarchies de-emphasizes the importance of cooperative network relations. In this paper; theory and hypotheses are developed explaining constraints on the emergence of opportunism when supplier-buyer relations are considered in a network context. The general thesis is that the opportunistic behavior of individual network suppliers relative to the dominant buyer; or hub firm, will decline at increasing levels of embeddedness in an interdependent supplier-buyer network, despite conditions of high asset specificity and small numbers bargaining.In recent years, the transaction cost economics perspective of Williamson (1975; has been adopted by organization theorists as one way of helping to explain vertical relations between organizations (c.f. Barney & Ouchi, 1986; Williamson & Ouchi, 198 I ;Hill, 1990). According to this view, the uncertainties of market relationships coupled with the bounded rationality of decision makers makes it likely that suppliers and buyers will seek to routinize their transactions by developing more established repeat relations with each other. However, such relations create mutual dependencies, based on what Williamson refers to as asset specificity and small numbers conditions. These conditions enhance the likelihood of opportunistic behavior, or "self-interest seeking with guile", resulting in intolerable transaction costs. When this happens, the market relationship will fail giving rise to a hierarchy (i.e. vertical integration). Transactions then become internalized, eliminating the uncertainty of the market and protecting against opportunism through a formal governance structure.One concern some writers have had with this line of thinking is that organizations that are not vertically integrated often do not engage in market-based relations with many of their suppliers or buyers, but instead, purposely establish and maintain long-term, cooperative, voluntary (i.e. non-owned) supply or distribution