For years, web-based learning systems have been widely employed in both educational and non-educational institutions. Although web-based learning systems are emerging as a useful tool for facilitating teaching and learning activities, the number of users is not increasing as fast as expected. This study develops an integrated model of instructor adoption of web-based learning systems by incorporating existing literature and multiple empirically verified theories, including the technology acceptance model and DeLone and McLean's information system success model. Survey data collected from 268 university instructors were examined using structural equation modeling to verify the proposed theoretical model. The research results further illuminate the factors that explain and predict the instructor adoption of web-based learning systems. Implications of this study are also discussed. (Contains 11 tables and 4 figures.)