The MCOTEA Operational Test and Evaluation Manual presents a process rooted in both the scientific method and Marine Corps operations. The manual combines elements of Marine Corps missions and tasks with systems engineering, decision analysis, and design of experiments to provide a process that supports all test and evaluation activities that MCOTEA performs. This second edition of the manual, which supersedes version 1.1, has been updated with significant new material on Reliability, Availability, and Maintainability as well as an in-depth section that sets forth, for the first time, a MCOTEA process for accrediting models and simulation. The overall test and evaluation process as established in version 1.1 has not changed apart from adjustments and clarifications based on lessons learned. The organization of the manual has been improved to better reflect and follow MCOTEA s six-step test and evaluation process. This manual is a living document and will be updated regularly with additional material. All hands are encouraged to submit comments or recommendations to the Scientific Advisor for the improvement of this manual. Use of this manual for performing Marine Corps operational test and evaluation is mandatory and effective immediately.