We examine the impact of power on the development of affective commitment in dyadic relations within a minimal exchange network. Theory stipulates that in repeated negotiated exchange (1) equal power and integrative bargaining issues increase the frequency of exchange between actors, (2) frequent exchange generates positive emotions that are attributed to the focal relation, and (3) positive emotion increases the propensity to form an affective commitment to the relation. When commitment develops, actors tend to remain in a relation despite alternatives and to provide benefits beyond those necessary to maintain the relationship. An experimental test supports the theory and suggests the conditions under which instrumental exchange relations become expressive. We discuss implications for the role of dyads in exchange networks.