PHYSICAL SECURITY IS DEFINED BY THE AUTHOR AS THE PHYSICAL MEASURES DESIGNED TO SAFEGUARD PERSONNEL; TO PREVENT UNAUTHORIZED ACCESS TO MATERIAL; AND TO PROTECT AGAINST SABOTAGE, DAMAGE, AND THEFT. PHYSICAL SECURITY ACTUALLY INCLUDES MORE THAN EXTERNAL SECURITY. SINCE ABSOLUTE SECURITY IS VIRTUALLY IMPOSSIBLE, PHYSICAL SECURITY MUST BOTH MAKE ACCESS SO DIFFICULT AS TO DETER AN INTRUDER, AND TO PROVIDE FOR AN INTRUDER'S APPREHENSION. THE CRITICALITY AND VULNERABILITY OF AN INSTALLATION MUST BE ASSESSED SO THAT PHYSICAL SECURITY NEEDS CAN BE DETERMINED. THE MAJOR SECURITY HAZARDS ARE THOSE RESULTING FROM NATURAL CAUSES, SUCH AS FLOODS OR EARTHQUAKES, OR THOSE WHICH ARE MAN-MADE, INCLUDING INDUSTRIAL ACCIDENTS, CIVIL DISTURBANCES, SABOTAGE, PILFERAGE, AND CARELESSNESS. THE USE OF PHYSICAL SECURITY FORCES IS DISCUSSED AS A SECURITY MEASURE. THESE FORCES ARE GIVEN THE RESPONSIBILITY OF PATROLLING THE FACILITY AND MONITORING PERSONNEL IDENTIFICATION AND MOVEMENT. TRAINING, SUPERVISION, AND VULNERABILITY TESTS ARE IMPORTANT ASPECTS OF THE SECURITY FORCES. THE USE OF SENTRY DOGS AS A SECURITY MEASURE IS OUTLINED. PHYSICAL PROTECTION REFERS TO THE SAFEGUARDS USED FOR PROTECTION OF A FIXED INSTALLATION. THESE SAFEGUARDS INCLUDE RESTRICTED AREA SECURITY -- LIGHTING, FENCES, AND LOCK AND KEY SYSTEMS. PERSONNEL IDENTIFICATION, VISITOR CONTROL, AND VEHICLE REGISTRATION AND PARKING ARE OTHER IMPORTANT ASPECTS OF FACILITY SECURITY. GUIDELINES FOR HANDLING BOMB THREATS ARE PROVIDED, ALSO FOR THE FORMULATION OF SECURITY AND DISASTER PLANS. PILFERAGE IS CITED AS ONE OF THE MOST FREQUENT AND MOST COSTLY TYPES OF SECURITY PROBLEMS. CONTROLS FOR SAFEGUARDING AGAINST BOTH EMPLOYEE AND CUSTOMER PILFERAGE ARE GIVEN. THE AUTHOR SUGGESTS THAT PHYSICAL SECURITY SURVEYS AND INSPECTIONS BE MADE PERIODICALLY, AND THAT EVERYONE INVOLVED IN THE SECURITY OF AN INSTALLATION SHOULD BE PROVIDED WITH SECURITY EDUCATION. A SUBJECT INDEX IS INCLUDED. (BAC)