AbstractThis article presents a summary of some of the issues and methods encountered in the use of multiple sensors for surveillance and tracking problems that arise in aerospace and defense. Applications include air traffic control using multiple internetted ground‐based radar sensors, ship‐based air defense systems, and air‐to‐air systems for drug interdiction and for air combat. During the past decade signal and data processing technology has evolved quickly, in terms of computing power, cost, size, and weight. As a result, the automatic fusion of data from multiple sensors has become a viable way of increasing the capabilities and performance of multiple target surveillance and tracking systems, while simultaneously reducing operator or pilot workload. The design, implementation, and performance of automated single sensor systems are fairly well understood, but the same cannot be said of systems that involve fusion of data from multiple sensors. A number of fundamental issues in this area remain unresolved, and the general problem is an area of active research in both the aerospace and the academic communities.