THE FIRST PHASE OF THE PROGRAM WAS COMPLETED IN FISCAL YEAR 1973 AND CONCERNED WEAPONS THAT EMPLOY ENERGY AS THE EFFECTS MECHANISM. THE TREATMENT OF OTHER EFFECTS MECHANISMS (CHEMICAL AND ELECTRICAL) WAS GENERAL. DETAILED WORK WAS COMPLETED IN THE MIDDLE PART OF 1975. A MULTIDISCIPLINARY PANEL OF SCIENTIFIC AND LAW ENFORCEMENT PERSONNEL DEVELOPED STANDARD SETTINGS OR SCENARIOS IN WHICH LESS-LETHAL WEAPONS ARE LIKELY TO BE EMPLOYED. ONCE STANDARD SCENARIOS WERE ESTABLISHED, DESIRED GOALS OR OBJECTIVES TO BE ACHIEVED BY THE USE OF LESS-LETHAL WEAPONS IN THESE SCENARIOS WERE ENUMERATED. DATA COLLECTED ON THE RESULTS OF EMPLOYING LESS-LETHAL WEAPONS, SUCH AS TISSUE DAMAGE AND PHYSIOLOGICAL RESPONSE, WERE THEN EXAMINED BY A MEDICAL GROUP. A BEHAVIOR ANALYSIS GROUP FURTHER EXAMINED THE BASIC DATA AND VIEWED AVAILABLE FILMS OF ACTUAL LESS-LETHAL WEAPON USES AND AUGMENTED THE FINDINGS OF THE MEDICAL GROUP. MOST PROJECTILE (NONCHEMICAL) DEVICES RELY ON PAIN AS THEIR MECHANISM OF EFFECTIVENESS. DISREGARDING PSYCHOLOGICAL EFFECTS OF PAIN, THE PROBABILITY OF ACHIEVING MISSION OBJECTIVES THROUGH PHYSIOLOGICAL RESPONSE AT KINETIC ENERGY LEVELS OF LESS-LETHAL WEAPONS IS RELATIVELY LOW (10 TO 20 PERCENT). FOR SMALL, RELATIVELY HARD PROJECTILES, AN AVAILABLE KINETIC LEVEL OF 15 TO 30 FOOT-POUNDS CANNOT BE EXCEEDED WITHOUT ENCOUNTERING SOME GROSS PHYSIOLOGICAL DAMAGE TO CRITICAL BODY ORGANS. CONSIDERING DAMAGE TO CRITICAL ORGANS, PENETRATION PROBLEMS, AND THE SIZE OF THE EYE SOCKET, IT APPEARS THAT AN OBJECT OF ABOUT 2 INCHES IN DIAMETER IS THE LEAST DAMAGING FOR A GIVEN KINETIC ENERGY LEVEL. THE RELATIONSHIP BETWEEN SKIN DAMAGE SEVERITY AND CRITICAL ORGAN DAMAGE IS PROJECTILE-DEPENDENT. UNDESIRABLE EFFECTS MAY BE OBTAINED FROM CHEMICAL ITEMS, NOT NECESSARILY THROUGH THE ACTION OF THE CHEMICAL AGENT ITSELF BUT THROUGH THE DELIVERY SYSTEM. ELECTRICAL DEVICES APPEAR TO BE THE MOST PROMISING IN TERMS OF MINIMIZING DAMAGE AND MAXIMIZING EFFECTIVENESS. ALTHOUGH NOT NORMALY THOUGHT OF AS LESS-LETHAL ITEMS, PENETRATING ITEMS ARE OFTEN ARE OFTEN NONLETHAL. PENETRATION-TYPE PROJECTILES SUCH AS THE STANDARD 0.38 CALIBER BULLET ARE NOT FULLY EFFECTIVE. A BIBLIOGRAPHY IS PROVIDED, AND ADDITIONAL INFORMATION ON THE RESEARCH PROGRAM IS APPENDED. (DEP)