The evaluation of information system effectiveness has been recognized as critically important not only in academic research but also in practice. However, directly quantifying information system effectiveness is extremely difficult because it must be measured after controlling for the influence of numerous variables that affect organizational performance. Consequently, researchers have frequently used user satisfaction—the degree to which an information system adequately provides the information users require—as a surrogate measure of information system effectiveness. However, prior studies using user satisfaction have often produced conflicting results. This study reexamines existing research on user satisfaction, develops a conceptual model, and empirically tests this model using middle managers at Korea Telecom as subjects. In the existing literature, user satisfaction has been used in three different conceptual senses: user attitude, information quality, and information system effectiveness, each of which has been studied based on different theoretical backgrounds and research objectives. The empirical results reveal that information quality is a key variable explaining both usage and information system effectiveness. However, contrary to expectations, the relationship between user attitude and usage, as well as the relationship between usage and information system effectiveness, were found to be insignificant. The lesson for subsequent studies using user satisfaction to evaluate information system effectiveness is that the phenomenon under evaluation must be precisely identified in advance. Furthermore, various policies adopted in practice to promote information system usage will produce synergistic effects when accompanied by improved information quality.