Most automobiles carry one person and are used for less than one hour per day. A more economically rational approach would be to use vehicles more intensively. Carsharing, in which people pay a subscription plus a per-use fee, is one means of doing so. Carsharing may be organized through affinity groups, large employers, transit operators, neighborhood groups, or large carsharing businesses. While carsharing does not offer convenient access to vehicles, it does provide users with a large range of vehicles, fewer ownership responsibilities, and less cost (if vehicles are not used intensively). Societal benefits include less demand for parking space and the indirect benefits resulting from costs being more directly tied to actual usage and vehicles being matched to trip purpose. This article reviews the experience with shared-use vehicle services and explores their prospects for the future, focusing on the trend toward expanded services and use of advanced communication and reservation technologies.