WITHIN THE CONCEPTUAL LEVEL MATCHING MODEL, INDIVIDUAL DIFFERENCES AMONG DELINQUENTS ARE DESCRIBED AS FALLING ALONG A CONTINUUM OF CONCEPTUAL COMPLEXITY, RANGING FROM CONCRETE TO ABSTRACT. THE ASPECT OF THE ENVIRONMENT MOST RELEVANT TO THIS CONTINUUM IS CONSIDERED TO BE THE DEGREE OF STRUCTURE. WITHIN THIS FRAMEWORK, IT IS POSSIBLE TO PREDICT THEORETICALLY MATCHED OR MISMATCHED ENVIRONMENTS FOR INDIVIDUALS AT A PARTICULAR CONCEPTUAL LEVEL. EVIDENCE OF THE UTILITY OF THIS MODEL IN EDUCATIONAL AND THERAPEUTIC APPLICATIONS IS REVIEWED, AND DATA FROM AN APPLICATION TO DELINQUENCY TREATMENT ARE PRESENTED. IN THE DELINQUENCY TREATMENT RESEARCH, THE MATCHING MODEL WAS USED IN THE ASSIGNMENT OF 43 ADOLESCENT DELINQUENTS TO EXISTING RESIDENTIAL TREATMENT PROGRAMS AND IN THE RESTRUCTURING OF THE PROGRAMS IN SUCH A WAY THAT FOUR THEORETICALLY DEFINED SUBGROUPS WERE CREATED. THE THEORETICAL EXPECTATIONS OF THE MATCHING MODEL WERE SUPPORTED BY BEHAVIORAL ADJUSTMENT RESULTS DURING AND AFTER RESIDENTIAL TREATMENT. FOR EXAMPLE, AFTER RETURNING TO THE COMMUNITY, BOYS FROM THEORETICALLY MATCHED TREATMENT ENVIRONMENTS HAD FEWER INCIDENCES OF PROBLEM BEHAVIOR THAN DID BOYS FROM THEORETICALLY MISMATCHED TREATMENT ENVIRONMENTS. STUDY FINDINGS HAVE IMPLICATIONS FOR BOTH RESEARCH AND PRACTICE. MOST IMPORTANTLY, THE STUDY DEMONSTRATES THE VALUE OF ASSIGNING YOUTHS AT THE LEAST MATURE, MOST CONCEPTUALLY SIMPLE STAGE OF DEVELOPMENT (CHARACTERIZED BY FAILURE TO INTERNALIZE CULTURALLY ACCEPTED BELIEFS AND VALUES AND BY ATTEMPTS TO DEFINE THE SELF IN OPPOSITION TO THESE BELIEFS AND VALUES) TO HIGHLY STRUCTURED TREATMENT ENVIRONMENTS. SUPPORTING DATA AND A LIST OF REFERENCES ARE INCLUDED. (AUTHOR ABSTRACT MODIFIEDL--LKM)