Web-based knowledge communities (WKCs) allow individuals with similar interests to collectively engage in knowledge acquisition and exchange. In spite of increased research interest in the topic of on-line knowledge exchange and social interaction, few studies have identified factors that contribute to WKC success. In this study we apply Preece?s community success framework of usability and sociability and the Information System (IS) success model as conceptual foundations for an investigation into the factors that lead to WKC success. We present and empirically test a research model for WKC success using survey data from an IT-related WKC. We find that both usability and sociability factors have a significant effect on user satisfaction which leads to increased sense of community and a greater frequency of WKC usage. This research is one of the first attempts to empirically examine Web-based knowledge community success. The implications for research and practice are also discussed.