A major portion of the problems associated with software development might be blamed on the lack of appropriate tools to aid in the planning and testing phases of software projects. As one step towards solving this problem, this paper presents a model to estimate the number of bugs remaining in a system at the beginning of the testing and integration phases of development. The model, based on software science metrics, was tested using data currently available in the literature. Extensions to the model are also presented which can be used to obtain such estimates as the expected amount of personnel and computer time required for project validation.