This collection of original research provides a comprehensive survey of developments at the leading edge of concurrent object-oriented programming. It documents progress—from general concepts to specific descriptions—in programming language design, semantic tools, systems, architectures, and applications. Chapters are written at a tutorial level and are accessible to a wide audience, including researchers, programmers, and technical managers. The problem of designing systems for concurrent programming has become an increasingly important area of research in computer science with a concomitant increase in the popularity of object-based programming. Because parallelism is a natural consequence of the use of objects, the development of systems for concurrent object-oriented programming is providing important software support for a new generation of concurrent computers.