IDEALLY, EVALUATIONS SHOULD FOLLOW A LOGICAL PROCESS, EXAMINING THEORETICAL ASSUMPTIONS, PROGRAM COMPONENTS, SUCCESS AND IMPACT, AND MODIFICATIONS SUGGESTED BY THE EVALUATION. HOWEVER, THIS PROCEDURE IS RARELY USED FOR EVALUATION OF JUVENILE DELINQUENCY PREVENTION PROGRAMS LARGELY BECAUSE MOST OF THESE PROGRAMS HAVE NO EXPLICIT THEORETICAL RATIONALE. EVALUATIONS OF DELINQUENCY PREVENTION PROGRAMS FUNDED BY THE DEPARTMENT OF HEALTH, EDUCATION, AND WELFARE DEMONSTRATED THAT MANY PROJECTS WERE DEVELOPED WITHOUT REFERENCE TO HEW'S SUGGESTED THEORETICAL MODEL, BUT WERE SIMPLY OLD APPROACHES, SUCH AS COUNSELING, DRESSED UP TO RESEMBLE THE NEW GUIDELINES. THIS LACK OF A THEORETICAL RATIONALE UNDERMINES A PROGRAM AND ITS EVALUATION BY AFFECTING THE CONCEPTUALIZATION AND IMPLEMENTATION OF PROGRAM OBJECTIVES, ENCOURAGING RELIANCE ON RECIDIVISM AS THE SINGLE CRITERION FOR SUCCESS, AND REDUCING THE VALIDITY OF ANY CONCLUSIONS THAT ARE DEDUCED FROM SUCCESS OR FAILURE IN ACHIEVING OBJECTIVES. IN ANY CASE, MOST PROJECTS IGNORE THE RECOMMENDATIONS OF THE EVALUATION, SINCE PRACTITIONERS TEND TO CONCENTRATE ON IMMEDIATE PROBLEMS AND DO NOT APPRECIATE THE RELEVANCE OF THEORY. BECAUSE OF THIS ATHEORETICAL ORIENTATION, DELINQUENCY EVALUATION STUDIES USUALLY RELY ON PRE-EXPERIMENTAL AND QUASI-EXPERIMENTAL DESIGNS EVEN THOUGH OBSERVATIONS OF SEVERAL PROGRAMS SUGGEST THAT RANDOMIZED FIELD EXPERIMENTAL DESIGNS CAN BE FEASIBLE AND WILL PRODUCE DEFINITIVE EVALUATION RESULTS. RESEARCH INTO THEORIES AND PRIOR STUDIES COULD REDUCE PROBLEMS INVOLVING THE TIMING OF OBSERVATIONS AND MEASURES. THE ABSENCE OF EXPLICIT THEORY AND INADEQUATE RESEARCH DESIGNS FURTHER CONTRIBUTE TO MEASUREMENTS AND ANALYSIS DIFFICULTIES. SINCE OFFICIAL STATISTICS REFLECT ONLY A SMALL PORTION OF DELINQUENT ACTS COMMITTED, THE WIDESPREAD USE OF RECIDIVISM TO MEASURE DELINQUENT BEHAVIOR IS A PARTICULAR PROBLEM. EVALUATIONS TEND TO CONCENTRATE ON COMPARISONS BETWEEN PROGRAM PARTICIPANTS AND CONTROL GROUPS, OBSCURING OTHER FINDINGS ON THE IMPACT OF THE PROGRAM ON DIFFERENT SUBGROUPS OF PARTICIPANTS. EXAMPLES OF EVALUATIONS ARE PRESENTED THROUGHOUT THE TEXT. REFERENCES ARE PROVIDED. (MJM)