This SGER proposal describes investigates issues of middleware interoperability in an international context through a targeted study on integrating NINF-G, a standards-based Grid RPC API software package, with the NSF Middleware Initiative (NMI) software system. NINF-G is developed and supported by Japan's National Institute of Advanced Industrial Science and Technology (AIST) and widely used internationally. Work involves integrating NINF-G into SDSC's Rocks clustering toolkit and the next NMI distribution. AIST is providing resources to create and execute a "build and test" environment to support this integration and ongoing maintenance and support.