A network of supercomputers and high-performance workstations appears to be the only reasonable way to provide adequate computing resources for the Grand Challenge problems of the next century. Such a collection of computers and supporting software environments is called a virtual computing environment (VCE). This paper describes the motivation and goals of the VCE project, followed by a description of the system. The paper concentrates on the runtime aspects of the VCE, and concludes with a discussion of a small prototype system that has been built using the Isis distributed toolkit. 1 Why Build A Virtual Computer? Advances in software technology have produced tools and environments for the development of parallel and distributed applications. These advances have resulted in the proliferation of a large number of different architectural classes like SIMD computers, MIMD computers, vector computers, etc., where each class represents a set of different trade-offs in design decisions. E...