Peer-to-Peer, or P2P sharing has gone through fast growth in recent years and drawn the interests of Information Systems (IS) researchers. However, there is a lack of empirical study on the individual's behavior of using P2P sharing software. Given the current existence of various uncertainties in P2P sharing, it is crucial to understand the factors that affect individual's usage of P2P sharing software. In this paper, we develop and empirically test a usage intention model which includes trust in the vendor of P2P sharing software and perceived risk as two major antecedent beliefs to the usage intention. Several trust antecedents are also identified in the model. Our preliminary results show the support for the model, and offer some important implications for software vendors in P2P sharing industry and regulatory bodies.