The purpose of this study is to find factors influencing bank customers' usage of Internet Banking in Korea and the U.S. The development of our research model is based on the theory of reasoned action, the theory of planned behavior, the technology acceptance model and the diffusion theory. We collected the empirical data by Internet survey questionnaire, and tested the research model using structural equation modelling method. The results of the structural model suggest that Internet Banking usage intention is enhanced by Internet Banking usage and perceived usefulness of Internet Banking in Korea. In addition, Internet Banking usage is influenced by compatibility and enjoyment in Korea. Internet Banking usage intention is effected by Internet Banking usage, perceived risk, and perceived usefulness of Internet Banking in America. Finally Internet Banking usage is affected by perceived usefulness and risk in America. This study examines the differences in constructs within the proposed model between Korean and American. The results show that there are no significant differences in Internet Banking usage and usage intention between Korean and American samples. However, t-test analyses reveal significant differences in perceived ease of use, perceived usefulness, compatibility, enjoyment, and perceived risk between Korean and American samples. Thus, this study contributes to the formulation of their Internet Banking strategies.