In this paper, the process migration facility in the Eindhoven multiprocessor system (EMPS) is presented. In the EMPS system, mailboxes are used for interprocess communication. These mailboxes provide transparency of location for communicating processes. The major advantages of mailbox communication in the EMPS system are (1) interprocess communication can proceed without losing messages and (2) the communication paths can be updated very efficiently when a process moves to another processor: By redirecting the mailbox connection of the migrating process, the communication paths of all processes connected to the same mailbox are updated. By measurements and a detailed evaluation of the performance it is demonstrated that intra-node process migration in the EMPS system is significantly more efficient than process migration in other distributed systems. The performance measurements of inter-node process migration yield results that can be favourably compared to other distributed systems.