A computer simulation model is a valuable tool in the evaluation of a developing hardware program and as a diagnostic/simulation aid for an ongoing production system. Hamilton Standard has developed a G189A simulation model to investigate the performance of a Space Station Extravehicular Mobility Unit (SSEMU). The SSEMU, also known as the Advanced Extravehicular Mobility Unit (AEMU), is in a hardware selection phase and further studies are beneficial to evaluate system performance using various subsystem candidates and integration schemes. Several subroutines representing newly developed subsystems have been Incorporated Into G189A for use in this model. These subroutines are: a Thermoelectric Condensing Heat Exchanger, a Regenerable Non-venting Thermal Sink, a Metal Oxide CO2 Removal/Dehumidification Subsystem, and the air Interactions In the suit volume. The Integration of particular components and subsystems within the SSEMU are evaluated using this software tool. in addition, the transient performance of the SSEMU is predicted for various modes of operation. The SSEMU computer simulation model and its applications are presented in this paper.