This paper addresses the effect of waste processing on advanced life support (ALS) system design. Waste processing is a critical component of an advanced life support system. It must take all life support system wastes and either convert them into useful products or into a form in which they can be discarded. Waste can be treated as soon as it is produced, stored as is, or processed into an intermediate form for further treatment. The decisions made will affect the cost-effectiveness of the system. Strategies must be developed to meet waste processing requirements for specific mission scenarios.