Based on the analysis of the original LCC model,a method is given for incorporating the effects of built-in test (BIT) into the life cycle cost of a given electronic system. An improved LCC model is given that captures the savings achieved by BIT through reducing the maintenance times , complexity of extemal test equipment , personnel skill levels , amount of spare parts , and the need for preventive maintenance. The model also includes such design considerations as false alarms , diagnostic errors , undetected faults , BIT hardware failures , and diagnostic ambiguity.