In peer-to-peer (P2P) systems, computers from around the globe share data and can participate in distributed computation. P2P became famous, and infamous, due to file-sharing systems like Napster. However, the scalability and robustness of these systems make them appealing to a wide range of applications.This paper introduces P-Ring, a new peer-to-peer index structure. P-Ring is fully distributed, faulttolerant, provides load balancing and logarithmic search performance, while supporting both equality and range queries. Our theoretical analysis as well as experimental results obtained both in a simulated environment and on PlanetLab, show the performance of our system.