A key challenge in peer-to-peer computing system is to provide decentralized and yet reliable services on top of a network of loosely coupled, weakly connected and possibly unreliable peers. This paper presents an effective dynamic passive replication scheme designed to provide reliable multicast service in Peer-Cast, an efficient and self-configurable peer-to-peer End System Multicast (ESM) system. We first describe the design of a distributed replication scheme, which enables reliable subscription and multicast dissemination of information in an environment of inherently unreliable peers. Then we present an analytical model to discuss its fault tolerance properties, and report a set of initial experiments, showing the feasibility and the effectiveness of the proposed approach.