The cost of reengineering of object-oriented software is often significantly less than the cost of developing new software. Object oriented software systems are more reusable. Reengineering of software systems rather than developing new software will save precious time and resources. Reengineering reduces the cost of maintenance by increasing the software quality and reducing complexity.To justify reengineering, the cost of reengineering software must be estimated and compared with the cost of new software. The cost of reengineering depends upon many factors but major factors are the portion of the software (number of objects) to be reengineered and complexity (interrelationship between objects) of the software. In this paper efforts are done to present a reengineering cost estimation model. On the basis of this model, software managers can take a decision whether to maintain, reengineer or retire the software
