Several distributed systems and software packages allow the use of workstation clusters as a virtual machine. In general, the interfaces to these environments use different programming paradigms for parallel and distributed computing, e.g. multithreading within a multiprocessor workstation and message passing or remote procedure calls for distributed computing. Porting applications to other distributed systems is a difficult task and many different programming paradigms have to be learned. We introduce a uniform interface for parallel and distributed programming based on POSIX Threads. By providing a global data space we are able to raise the concept of threads to a higher level of concurrency - threads may be spread over several heterogeneous machines and are therefore called remote threads (RThreads). Up to now, we have implemented the RThread interface on top of PVM and DCE