Conceptual designs for initial, intermediate, and advanced lunar base life support systems (LSS) are under development at JSC. The initial air revitalization, water recovery, and waste management subsystems are based on space station technologies. The intermediate system expands on the initial capabilities; for example, the initial waste management subsystem allows only for compacting and storing solid waste, while the intermediate waste management subsystem includes measures for recovering useful substances from the waste. The advanced system includes biological waste treatment and higher plants to be used for air revitalization and water processing.This paper describes the three systems and discusses the basis for selecting individual processes. System-level mass balances are used to illustrate the interaction of the air, water, and waste loops. The effect of introducing different waste treatment processes into the initial LSS is examined. The impact of biological waste treatment and higher plants on the air revitalization subsystem is also discussed.