The realization of relationship marketing requires cooperative exchange between buyers and sellers. A key determinant of cooperative exchange is the uncertainty perceived by the cooperating parties. This study investigates how cooperation is affected by decision makers' perception of uncertainties in the environmental context, in relationships, and in decision-making routines. A sample of 135 branch managers from banks is used in a LISREL model. The results show that uncertainty regarding relationships and decision making has strong direct effects on buyer-seller cooperation. Relationship and decision making, in turn, are affected by contextual uncertainty. The results highlight the importance of internal resources in firms in facilitating cooperation between buyers and sellers.