<div class="htmlview paragraph">The interacting processes and reconfigurable subsystems of the Space Station Freedom Environmental Control and Life Support System (ECLSS) present a tremendous technical challenge to Freedom's crew and ground support. E<span class="small-caps">CLSS</span> operation and problem analysis is time-consuming for crew members and difficult for current computerized control, monitoring, and diagnostic software.</div> <div class="htmlview paragraph">These challenges can be at least partially mitigated by the use of advanced techniques such as Model-Based Reasoning (MBR). This paper will provide an overview of MBR as it is being applied to Space Station Freedom <span class="small-caps">ECLSS</span>. It will report on work being done to produce intelligent systems to help design, control, monitor, and diagnose Freedom's <span class="small-caps">ECLSS</span>. Specifically, work on predictive monitoring, diagnosability, and diagnosis, with emphasis on the automated diagnosis of the regenerative water recovery and air revitalization processes will be discussed.</div>