Testing of the International Space Station (ISS) U.S. Laboratory baseline configuration of the Atmosphere Revitalization Subsystem (ARS) by NASA's Marshall Space Flight Center (MSFC) has been conducted as part of the Environmental Control and Life Support System (ECLSS) design and development program. This testing addressed specific questions with respect to the control and performance of the baseline ARS subassemblies in the ISS U.S. Laboratory configuration. The test used pressurized oxygen injection, a mass spectrometric major constituent analyzer (MCA), a four-bed molecular sieve carbon dioxide removal assembly (CDRA), and a trace contaminant control subassembly (TCCS) to maintain the atmospheric composition in a sealed chamber within ISS specifications. Human metabolic processes for a crew of four are simulated according to projected ISS mission timelines.The Integrated ARS Test (IART) builds upon previous integrated ECLSS testing conducted at MSFC between 1987 and 1992. The IART is designed to address ARS control and performance issues that are peculiar to the ISS. These issues resulted from the ISS ECLSS configuration development, design requirement changes since 1992, and the increased maturity of each ARS subassembly's design. IART test objectives, facility design, pretest analyses, test and control requirements, and test results are presented.