Distributed event-based systems (DEBS) are gaining increasing attention in new application areas such as transport information monitoring, event-driven supply-chain management and ubiquitous sensor-rich environments. However, as DEBS increasingly enter the enterprise and commercial domains, performance and quality of service issues are becoming a major concern. While numerous approaches to performance modeling and evaluation of conventional request/reply-based distributed systems are available in the literature, no general approach exists for DEBS. This paper is the first to provide a comprehensive methodology for workload characterization and performance modeling of DEBS. A workload model of a generic DEBS is developed and operational analysis techniques are used to characterize the system traffic and derive an approximation for the mean event delivery latency. Following this, a modeling technique is presented that can be used for accurate performance prediction. The paper is concluded with a case study of a real life system demonstrating the effectiveness and practicality of the proposed approach.