The current status of the space station (SS) environmental control and life support system (ECLSS) design is outlined. The concept has been defined at the subsystem Level. Data supporting these definitions are provided which identify general configurations for all modules. Requirements, guidelines and assumptions used in generating these configurations are detailed. The basic 2 US module “core” space station is addressed along with system synergism issues and early man-tended and future growth considerations. Along with these basic studies, also addressed here are options related to variation in the “core” module makeup and more austere station concepts such as commonality, automation and design to cost.