Community information systems have the power to transform communities. However, without fully understanding the factors affecting community information system viability, and the complex relationships between these factors, communities struggle to manage such projects in a way that leads to viable systems that deliver real benefits. This paper develops a Model of Community Information System Viability, based on both existing literature and the study of three community information system projects. This Model represents not only the generic factors that inform viability, but also considers the impact of community context.