This paper discusses the concept of adaptability as a mearwfor reaping the cost and schedule reduction benejits of reuse. Adaptability strives to implement the variability identified by domain analyses while managing the cost of implementation, extension, and use. The paper discusses a context for understanding dl~erent domain–specific reuse approaches relative to adaptability and anaiyzes e.rperience in designing and developing adaptable code. The experience is drawn from the ARPA Software Technology jbr Adaptable, Reliable Systems (ST~S) joint demonstratio