A maintenance management system is not a set of technical procedures for improving maintenance performance, but a means of ensuring that the correct activities are scheduled and performed at the right time and in an efficient and cost-effective manner. This manual presents guidelines for developing such a system for medium to large water supply and sanitation organizations in developing countries. The guidelines do not present rigid procedures, but basic principles and practices, along with a discussion, where appropriate, of alternative approaches. The manual recognizes that each case is different and tries to help the reader grasp the essential elements and adapt the details to his or her own situation. Examples, forms, and illustrations from a variety of countries are included. The manual covers the following elements of a complete maintenance management system: (1) planning and organizing, including goal setting, task identification and description, resource requirements, annual plan and schedule, and staff organization and training; (2) work order systems; (3) equipment records; (4) materials inventory controls, and (5) monitoring, evaluating, and reporting. A detailed list of references is included, along with appendices which provide additional examples, blank forms, sample planning, budgeting, and recordkeeping techniques, a list of training resources, and brief discussions of computerized maintenance management and the contracting of maintenance services. (Author abstract, modified).