Parallel Virtual Machine (PVM) is a widely-used software system that allows a heterogeneous set of parallel and serial UNIX-based computers to be programmed as a single distributed-memory parallel machine. In this paper, an extension to PVM to support dynamic process migration is presented. Support for migration is important in general-purpose workstation environments since it allows parallel computations to co-exist with other applications, using idle-cycles as they become available and off-loading from workstations when they are no longer free. A description and evaluation of the design and implementation of the prototype Migratable PVM system is presented together with some performance results. 1 Introduction PVM [1, 2, 3] is a software system that allows a heterogeneous network of parallel and serial computers to be programmed as a single computational resource. This resource appears to the application programmer as a potentially large distributed-memory virtual computer. Such a s...