As the importance of relational exchange over discrete exchange has been increasingly emphasized, research on relational norms has grown in significance. This study proposes the hypothesis that in ongoing buyer-seller exchange relationships, when power structures are imbalanced rather than balanced, not only bureaucratic structuring but also relational norms as a complementary mechanism will be more pronounced. In a study of buyers and suppliers in the Korean electrical and electronic components industry, the hypothesis that norms would be higher under imbalanced power structures than under balanced ones was partially supported. Specifically, flexibility norms and reciprocity norms were higher when the power structure was imbalanced rather than balanced. Regarding bureaucratic structuring, only formalization was found to be higher in imbalanced power relationships than in balanced ones.