In this research we investigate the possibility of designing a user interface for electronic commerce systems that will evoke target feelings in the customer. The focus is on the impact of visual design factors on the feeling of trustworthiness because of its significant effect upon the behavior of customers using electronic commerce systems. Four empirical studies were conducted in the domain of cyber-banking systems. The subjects were cyber-banking system developers, bank personnel and potential customers of cyber-banking systems in Korea ranging in age from late teens to early forties. The first study was directed at developing the self-report questionnaire that faithfully reflects the emotional factors related to cyber-banking systems. The resulting questionnaire consisted of the forty bipolar emotive differential scales representative of the emotions most important in interacting with cyber-banking systems, e.g. reliable-not reliable. The second study focused on determining the important visual design factors from the customer's perspective. Fourteen design factors identified from subjects' descriptions were classified into the four design categories of title, menu, main clipart and color. The third study investigated the correlations between the emotional factors and design factors. The design factors were found to have significant effects upon the extent of feelings related to symmetry, trustworthiness, awkwardness and elegance. In the final study, two interfaces were designed based on the results of the third study to differentiate the extent of trustworthiness evoked. The results indicate that it is possible to manipulate the visual design factors of the customer interface in order to induce a target emotion, such as trustworthiness. The paper concludes by discussing the implications of the empirical results on the design and implementation of customer interfaces to electronic commerce systems in general.