The development of the Advanced Life Support (ALS) Sizing Analysis Tool (ALSSAT) using Microsoft® Excel was initiated by the Crew and Thermal Systems Division of the NASA Johnson Space Center (JSC) in 1997 to support the ALS and Exploration Offices in Environmental Control and Life Support System (ECLSS) design and studies. It aids the user in performing detailed sizing of the ECLSS for different combinations of Exploration Life Support (ELS) regenerative system technologies. This analysis tool will assist the user in performing ECLSS preliminary design and trade studies as well as system optimization efficiently and economically. The latest ALSSAT related publication in ICES 2004 detailed the development status of ALSSAT including the completion of all six ELS subsystems (ELSS), namely, the Air Management Subsystem, Biomass Subsystem, Food Management Subsystem, Solid Waste Management Subsystem, the Water Management Subsystem, and the Thermal Control Subsystem as well as two external interfaces, including the Extravehicular Activity and Human Accommodations. Since 2004, many more regenerative technologies in the ELSS have been implemented into ALSSAT. ALSSAT has also been used for the ELS Research and Technology Development (R&TD) Metric Calculation for fiscal year 2002 (FY02) through FY06. It was also used to conduct the Lunar Outpost Metric calculation for FY08 and was integrated as part of a Habitat Model that was developed at the NASA Langley Research Center to support the Constellation Program. This paper will give an update on the current development status of the ALSSAT as well as present the analytical results of one of the trade studies that was performed.