Abstract. Information Services are fundamental blocks of the Grid infrastructure. They are responsible for collecting and distributing information about resource availability and status to users: the quality of these data may have a strong impact on scheduling algorithms and overall performance. Many popular information services have a centralized structure. This clearly introduces problems related to information updating and fault tolerance. Also, in very large configurations, scalability may be an issue. In this work, we present a Grid Information Service based on the peerto-peer technology. Our system offers a fast propagation of information and has high scalability and reliability. We implemented our system complying to the OGSA standard using the Globus Toolkit 3. Our system can run on Linux and Windows systems, with different network configurations, so to trade off between redundancy (reliability) and cost.