Abstract: The RenderMan Interface specification proposed by Pixar is a standard for communication between modeling software and rendering software or devices. This standard has proven very powerful and is extremely popular in production work. Although the standard itself claims not to specify a rendering algorithm, people have speculated RenderMan and global illumination are mutually incompatible. We have implemented a rendering system which fully adheres to the RenderMan Interface and uses global illumination algorithms. Specifically, this implementation supports progressive refinement radiosity and distribution ray tracing in a two-pass approach. This rendering system is widely distributed, very popular, and has been used in production (three properties usually not found in global illumination renderers). We discuss how we overcame problems in mating global illumination algorithms with the RenderMan standard, and make recommendations for future versions of the standard to better accommodate such algorithms. We also present a summary of important lessons we learned by creating and distributing this tool.