The International Space Station (ISS) Program has been divided into three distinct stages. The first phase of the program performs risk mitigation experiments during the joint Shuttle - MIR missions. The second stage establishes a point in the program where the United States Laboratory will have the capability to support initial research, the Italian Mini-Pressurized Logistic module will provide the capability to help resupply the ISS and the United States Node and Laboratory module in conjunction with the Russian Functional Cargo Block (FGB) and Service Module (SM) will have the capability to support up to three crew members continuously on-orbit. The final phase of the program will complete the Russian and the U.S. segments and will add the Japanese and the European modules to ISS. At the end of stage three ISS will also have the capability to support up to six crew members continuously.Phase one is currently preparing for the third flight to MIR while phase two is in the manufacturing phase. This paper provides an overview of the Environmental Control and Life Support (ECLS) System that will support life during the second phase.