E-commerce enables information sharing that strengthens supply chain relationships. However, different forms of digital relationships, like EDI and e-marketplaces, present different challenges. EDI involves high setup costs but low monitoring and transaction costs with high information sharing and interdependency between buyers and suppliers. This reduces opportunities for opportunism. E-marketplaces have lower setup costs but higher monitoring and transaction costs with less information sharing and interdependency, allowing more opportunities for opportunism. The optimal relationship form depends on factors like product complexity, environmental uncertainty and concentration, and dynamism. Building effective long-term supplier relationships requires considering both digital options and strategic business needs.