This paper presents a methodology for, and an evaluation of the feasibility of converting a typical data processing system to a data base management system. This methodology is applied to a particular system. The data base management system under evaluation uses a back-end mini-computer to perform the data management functions. The evaluation is made in terms of changes in system resources, program requirements, and human factors. The results of this study provide considerable insight into the problem of conversion to a data base management system, and suggest guidelines for the evaluation of any proposed data base conversions.