Marine Corps Reference Publication (MCRP) 3-40A.5, Health Service Support Field Reference Guide, expands on the doctrine established in Marine Corps Tactical Publication 3-40A, Health Service Support Operations. This publication provides information on the concept of employment of health service support (HSS) units (medical and dental elements) in an operational environment and provides specific tactics, techniques, and procedures for medical personnel who are supporting Marine Corps operating forces. MCRP 3-40A.5 provides commanders of medical units, commanders of units with organic medical and dental elements and their staffs, and United States Navy medical augmentation personnel with information that allows them to better understand the Marine Corps HSS system. This publication has been prepared as an instructional and doctrinal guide for medical and dental personnel, with and without previous Marine Corps operating forces experience.