This article contributes to the emerging literature on transparency by developing and empirically testing a theoretical framework that explains the determinants of local government Web site transparency. It aims to answer the following central question: What institutional factors determine the different dimensions of government transparency? The framework distinguishes three dimensions of transparency—decision making transparency, policy information transparency, and policy outcome transparency—and hypothesizes three explanations for each: organizational capacity, political influence, and group influence on government. Results indicate that each dimension of transparency is associated with different factors. Decision-making transparency is associated with political influence; when left-wing parties are strong in the local council, local government tends to be more transparent. Policy information transparency is associated with media attention and external group pressure, and policy outcome transparency is associated with both external group pressure and the organizational capacity. The authors discuss the implications for policy and administration.