The purpose of this technical manual is provide facility managers with the information and procedures necessary to develop and update a preventive maintenance (PM) program for their facilities that is based on the reliability characteristics of equipment and components and cost. Such a PM program will help to achieve the highest possible level of facility availability at the minimum cost. The information in this manual reflects the commercial practices and lessons learned over many years of developing cost-effective preventive maintenance programs for a wide variety of systems and equipment. It specifically focuses on developing PM programs for electrical and mechanical systems used in command, control, communications, computer, intelligence, surveillance, and reconnaissance (C4ISR) facilities based on the reliability characteristics of those systems and economic considerations, while ensuring that safety is not compromised. The process for developing such a PM program is called Reliability-Centered Maintenance, or RCM. Two appendices develop key topics more deeply: appendix B, statistical distribution; and appendix C, availability.