ONE STRATEGY IS TO GATHER AGGREGATE DATA ON CRIME AND OTHER SOCIAL INDICATORS AND TO STUDY VARIATIONS IN CRIME THAT OCCUR BETWEEN JURISDICTIONS OR OVER TIME. ANOTHER STRATEGY ATTEMPTS TO ASSESS THE IMPACT OF CHANGES IN LAW ENFORCEMENT OR PUNISHMENT POLICY BY CLOSELY FOLLOWING WHAT HAPPENS AFTER PARTICULAR POLICY SHIFTS OCCUR. COMPARISONS IN REPORTED CRIME RATES ARE MADE BEFORE AND AFTER POLICY CHANGE. THE KANSAS CITY, MO., PREVENTIVE PATROL EXPERIMENT WAS PATTERNED AFTER THE LATTER STRATEGY TO STUDY DETERRENCE THROUGH THE ANALYSIS OR REAL POLICY CHANGE. THE EXPERIMENT SHOWED THAT PREVENTIVE PATROL HAS SOME VALUE IN REDUCING CRIME BUT, MORE IMPORTANTLY, CALLED ATTENTION TO PROBLEMS OF AND LIMITATIONS ASSOCIATED WITH FIELD EXPERIMENTATION. FIELD STUDIES IN LAW ENFORCEMENT HAVE RARELY BEEN UNDERTAKEN. QUASI-EXPERIMENTAL EVALUATION OF TOPICS SUCH AS VARIATIONS IN POLICE PATROL, PUNISHMENT FOR RAPE, THE INTRODUCTION OF PORTABLE BREATHALIZER TESTS, DRUNK DRIVING ENFORCEMENT, AND CONTROL OF SPEEDING ON HIGHWAYS HAS PRODUCED MIXED RESULTS. IT IS CLEAR, HOWEVER, THAT PROGRESS WILL BE SLOW AND EMPIRICALLY JUSTIFIED GENERALIZATIONS WILL BE DIFFICULT IF INTERVENTION EVALUATION IS TO BE THE PRIMARY BUILDING BLOCK FOR DETERRENCE THEORY. SKEPTICISM IS EXPRESSED OVER THE USE OF SOPHISTICATED STATISTICAL METHODS AS A MECHANISM FOR MEASURING DETERRENCE, BASED ON THREE PROBLEMS: (1) LACK OF INFORMATION ABOUT FACTORS THAT INFLUENCE VARIATIONS IN CRIME RATES OVER TIME AND BETWEEN AREAS, (2) LACK OF A CAPACITY TO CONTROL FOR THESE FACTORS, (3) THE PROBLEM OF DISTINGUISHING BETWEEN RELATIVELY HIGH PUNISHMENT RATES AS A CAUSE OF LOW CRIME RATES AND RELATIVELY LOW CRIME RATES AS A CAUSE OF HIGH PUNISHMENT RATES, AND (4) THE FACT THAT STUDIES USING SOPHISTICATED STATISTICAL METHODS SHED NO LIGHT ON THE ISSUE OF HOW SYSTEMS DIFFERING IN PUNISHMENT POLICY COME TO BE DIFFERENT. (DEP)