To remain competitive, software development organizations must reduce cycle time and cost, while at the same time adding function and improving quality. One potential solution lies in software reuse. Because software reuse is not free, we must weigh the potential benefits against the expenditures of time and resources required to identify and integrate reusable software into products. We first introduce software reuse concepts and examine the cost-benefit trade-offs of software reuse investments. We then provide a set of metrics used by IBM to accurately reflect the effort saved by reuse. We define reuse metrics that distinguish the savings and benefits from those already gained through accepted software engineering techniques. When used with the return-on-investment (ROI) model described in this paper, these metrics can effectively establish a sound business justification for reuse and can help assess the success of organizational reuse programs.