Abstract Today's large software-intensive systems have critical quality requirements, limited budgets, and stringent development and maintenance schedules. It is therefore necessary to be able to objectively evaluate these systems during their development to determine whether they will meet requirements, schedule, and budget, to assist risk management, and to facilitate corrective and preventive action. The discipline of software metrics has the potential for providing the objective information necessary for technical and managerial insight into, and control of, the development effort. However, the current software metrics literature does not address the need for integrated and consistent system- and software-level metrics, nor does it provide detailed descriptions of metrics for full life cycle coverage. This article is an introduction to work in progress at The Aerospace Corporation and California State University, Long Beach, in the area of metrics for requirements engineering. The first in a planned series of papers on metrics for full life cycle system and software engineering, it describes the role of metrics in an integrated approach to system and software engineering, introduces the basic components of complete metric definitions, and discusses the use of metrics in comprehensively assessing objective aspects of the requirements engineering process and its products.