Citing a need for a strong, clearly-defined approach to software maintenance, this report emphasizes the importance of maintenance throughout the life cycle of a software system. It also stresses the need to plan, develop, use, and maintain a software system with future maintenance in mind. The report presents guidance for controlling and improving the software maintenance process and includes suggested criteria for deciding whether continued maintenance of a software system is justified. It concludes that an organization's software maintenance efforts can be improved through the institution and enforcement of software maintenance standards and techniques. A glossary of technical terms, a list of supporting ICST (Institute for Computer Sciences and Technology) publications, and a list of suggested additional readings are included. Appendices provide information on the software maintenance process; how to decide whether to continue maintaining a system; and software maintenance tools. The guidelines are intended for use by both managers and maintainers. A glossary and two brief lists of reports are provided. (THC)