Users may use a mobile service in various contexts. It is critical to study how users? perceptions and intentions are affected by context. At the same time, incentives such as financial rewards or mandatory usage policies may also affect users' behavior. We propose an acceptance model of mobile commerce with a consideration of context and incentive. We apply this model to the case of a GPSbased taxi-dispatching system. Preliminary data analysis illustrates that context and incentive have significant impacts on uses' behavior.