The International Space Station (ISS) is truly an international undertaking. The project is being led by the United States, with the participation of Japan, the European Space Agency, Canada, Italy, Russia, and Brazil. Russia is participating in full partnership with the United States in the fabrication of ISS modules, the assembly of ISS elements on orbit, and, after assembly has been completed, the day-to-day operation of the station. Construction of the ISS began with the launch of the Russian Zarya module in November 1998 followed by the launch of the U.S. Unity module in December 1998. The two modules were mated and interconnected by the crew of the Space Shuttle during the December flight, and the first assembled element of the ISS was in place. Construction will continue with the delivery of components and assembly on orbit through a series of 46 planned flights. During the study period, the Assembly Complete milestone was scheduled for November 2004 with the final ISS construction flight delivering the U.S. Habitation Module. Engineering Challenges to the Long-Term Operation of the International Space Station is a study of the engineering challenges posed by longterm operation of the ISS. This report states that the National Aeronautics and Space Administration (NASA) and the ISS developers have focused almost totally on completing the design and development of the station and completing its assembly in orbit. This report addresses the issues and opportunities related to long-term operations.