This study was initiated to adopt a new perspective on EDP internal control systems, departing from previous research frameworks, and to attempt an organizational contingency approach. The purpose was to demonstrate that EDP internal control systems are not only influenced by organizational contingency variables but also constitute important variables that significantly affect accounting information system performance. The study was conducted through in-depth interviews with IT managers and accounting information system users at 30 domestic manufacturing firms. The results revealed that among the structural variables of EDP internal control systems, the size of general controls, the type of general controls, the type of application controls, and the degree of EDP auditing are influenced by contingency factors such as organizational size and information system sophistication. Furthermore, it was demonstrated that the greater the fit between organizational contingency variables and the type of general controls, the higher the performance of the accounting information system.