Dynamic system models are being developed which track the flow of material through a regenerative life support system over time periods of months to years. These models, written in MATLAB/SIMULINK©, are designed to help perform system trade studies and to evaluate system operations issues. They include atmosphere regeneration, water recovery, crop growth, food processing, and waste processing. The overall system simulation is being used to quantify variations in stream flow rates and subsystem processing rates and to estimate buffer requirements for various system configurations and design options. It will also be used to investigate scheduling, operations, and control issues and to evaluate the sensitivity of system-level dynamics to model inaccuracies and off-nominal operation. Results will be presented on sharing or separating the atmospheres of the crew, crops, and waste chambers.