This study examines the internal controls of information systems, which constitute an important component of corporate internal control systems. Its primary objectives are to identify the variables that influence the characteristics of information system internal controls and to determine the causes of differences in the types and intensity of information systems across firms. The hypotheses tested comprise six propositions examining the relationships between three independent variables—environmental stability, information system size, and information system maturity—and two dependent variables representing information system internal control intensity and internal control methods. The survey targeted manufacturing and financial firms listed in the Listed Companies Directory. In univariate analysis, the results supported the hypotheses, showing that greater industry stability and larger information system size and maturity were associated with higher information system control intensity. In multivariate analysis, the information system maturity variable was found to have the greatest influence on information system internal control intensity. Regarding internal control methods, no significant differences were found attributable to the independent variables. Although there are limitations in the evaluation methodology for internal control intensity, this study holds significant value as the first systematic attempt to analyze the variables affecting information system internal controls using a relatively large sample of listed companies.