The establishment of EDI system significantly transforms the relationship among channel members. This study investigates the relationship between buying and selling companies who use the EDI system. The results of this study are summarized as follows. First, the establishment of the EDI system has a positive effect on the task effectiveness, cost and competitiveness regardless of buying and selling companies. Second, the establishment of EDI system does not affects direct and indirect trust in both companies. Third, the effects of task effectiveness and cost are not related with the perceived or behavioral trust.