Recently, Electronic Data Interchange (EDI) systems are widely used. Many organizations exchange the documents by using EDI, and EDI is used in various industries such as physical distribution, export and import business, custom, and medical care. However, there have been little attempt to empirically investigate the success factors of EDI system. In this paper, we identify the influencing factors which determine the success of typical information system and then suggest the additional factors characterized to the EDI system. Our research model, mainly based on the system success model, is tested by analyzing the empirical data acquired from the companies in the medical industry. As a result, the system quality, information quality, service quality, and the perceived sacrifice turned out to be significant to the success of EDI system while data security does not. The result of this research is likely to help providing useful guidelines for the successful EDI implementations.