Question Answering Systems (QAS) are receiving increasing attention from IS researchers, particularly those in the information retrieval and natural language processing communities. Evaluation of an IS's success and user satisfaction are important issues, especially for emerging online service systems using the Internet. Although many QAS have been implemented, little work has been done on the development of an evaluation model for them. Our purpose was to develop a validated instrument to measure user satisfaction with QAS (USQAS). The proposed validated instrument was intended as a reference for the design of QAS from a user's perspective.