A coherent approach to early and evolutionary habitat design for a lunar outpost is required. It should be based on the fundamental purpose of the habitat - to provide shelter, living and working space for humans. It is proposed that the existing “Man-Systems Integration Standards (MSIS),” (NASA, 1989) which was designed primarily as guidance for the Space Station, be the basis for the design approach for a lunar outpost. There are a number of differences between lunar outposts and space stations, stemming from their different environments and uses, which will have to be recognized. The MSIS for a lunar outpost should contain both upgraded general and specific requirements on which lunar outpost design should be based.