This paper describes an implementation of Java's Remote Method Invocation RMI that is designed to run on top of the Globus high performance computing protocol. The primary contribution of this work is to illustrate how the object serialization mechanism used by RMI can be extended so that it becomes more con gurable. This allows the implementation of object serialization protocols that are more e cient than the default or that are compatible with other distributed object models like HPC++, which is based on C++. Both issues are important when RMI is to be used in scienti c computing.