Many Korean banks and companies have adopted EDI to replace traditioanal paper documents by electronic ones, which can move much faster with greater accuracy, Also, it is expected to reduce overall costs and maintain good relationships with customers. However, in practice, the performance of EDI seems to be less than expected. The purpose of this paper is to identify the impact of environment and adoption factors on the performance of financial EDI. We proposed a model for the relationships based on the existing literature and peformed a survey of Korean commercial banks and companies using KTNET. The results of this study are as follows: First, the business environment represented by the size of companies and the frequency of transactions showed a negative impact on the performance in terms of efficiency, which is quite converse to the common belief. Second, the technical environment, including computing skills of users and operators, showed a positive impact on the performance in terms of effectiveness. Third, the clearer the adoption purpose, the higher is the performace as intended, while the initiative for the adoption process showed no significant impact.