The Space Station Freedom (SSF) program has as its objective the establishment of a permanently manned facility in low earth orbit. The facility is intended to be used for a wide range of activities and to accommodate a number of alternative growth paths. The current program design calls for the Space Station to be assembled on-orbit over a period of years during a series of Shuttle launched mission-builds (MB). This will require extensive integration and verification of the Space Station elements and systems throughout the build-up sequence. Each stage of Space Station assembly results in a complete spacecraft on orbit. As such, the SSF will be required to be completely self sufficient between rendezvous with the Orbiter. This paper will address the assembly and integration with regards to the Environmental Control and Life Support System throughout the assembly sequence including hardware interfaces and stage performance.