The purpose of this study is to examine the influence of antecedents on consumer's trust in online companies. Specifically, it aims to examine the relationship between perceptions about the company (including perceived size and perceived reputation) as well as perceptions about the Web site quality (including system quality, information quality, and service quality) on customer's trust in online company, and then on purchase intention. Results of these studies demonstrated that customer's trust in the online company is an important determinant of customer intention to purchase. Furthermore, the results confirmed that perceived size and Web site quality (including system quality, information quality, and service quality) were the principal determinant influencing consumer's trust in online company. Future, our study results could suggest practitioners can use these results as guidelines in website development, daily operations, and customer support processes in online business.