The collection of personal information from customers is a necessity for Internet merchants, who need such information to effectively provide service to customers. The ease with which data can be acquired and disseminated across the Web, and the peculiarities of the electronic environment have led to growing concerns from many potential customers over disclosing personal information to e-service providers. Self-disclosure theories suggest that consumers' willingness to disclose personal information is based on their assessments of the related costs, risks, and benefits. This study experimentally manipulated initial trust and the nature of the incentive given to encourage information disclosure. It also measured actual disclosure behavior rather than just intention or attitude. A key finding is that subjects did not claim to be more willing to provide information in the presence of incentives, but in fact, as indicated by their behavior, were more inclined to do so. What is more, privacy concern, involvement with the service category considered, and attitude toward on-line shopping act like antecedents for a willingness to share attitudinal measure but are not diagnostic of actual behavior.