The customer loyalty has been decreasing dramatically in e-Business environments such as cyber trading, shopping, banking, and portal services. However, little research has been done so far in order to analysis the newly emerging concept and changing nature of the e-Business customer loyalty. The purpose of this study is to investigate whether the quality of e-Business information systems has any impact on customer loyalty. The quality, which is tee independent construct in this study, is divided into three variables: basic system quality, information contents quality, and service quality. Cyber systems of 40 domestic stock trading firms were chosen as target e-Business information systems Both online survey and traditional field survey were employed in order to collect data, and more than 8,000 cyber customers have responded. The results of statistical analysis show that all of three independent variables have statistically significant effects on customer loyalty and, among three variables, the basic system quality has the strongest impact.