THE FINAL SAMPLE CONSISTED OF 161 NONDELINQUENTS AND 127 DELINQUENTS IN 3 CITIES: BALTIMORE, MARYLAND; INDIANAPOLIS, INDIANA; AND PHOENIX, ARIZONA. LEARNING DISABILITY (LD) IS CHARACTERIZED BY PRONOUNCED INTRAPERSONAL DIFFERENCES IN THE ABILITY TO PERFORM A VARIETY OF VERBAL, QUANTITATIVE, AND MANIPULATIVE TASKS RESULTING FROM SOME NONOBVIOUS INTERFERENCE WITH INFORMATION RECEIVING, PROCESSING, OR PRODUCTION. A TWO-STEP PROCEDURE WAS UTILIZED TO ASSESS LD. FIRST, A TRAINED REVIEWER EXAMINED SCHOOL AND CLINICAL RECORDS FOR EVIDENCE OF LD, MENTAL RETARDATION, OR EMOTIONAL DISTURBANCE. YOUTHS WERE EXCLUDED FROM THE SAMPLE FOR PHYSICAL HANDICAP, NATIVE LANGUAGE DIFFERENCES, MENTAL RETARDATION, OR EMOTIONAL DISTURBANCE. WHERE NO EVIDENCE OF LD WAS APPARENT, THE YOUTH WAS ASSIGNED TO A NON-LD GROUP. WHERE EVIDENCE WAS INDICATIVE OF LD, AN INDEPTH DIAGNOSTIC ASSESSMENT INCLUDING TESTS, OBSERVATIONS, AND INTERVIEWS WAS UNDERTAKEN TO FURTHER SCREEN OUT NON-LD YOUTHS. EXTENSIVE PRECAUTIONS WERE TAKEN TO ENSURE TIGHT QUALITY CONTROL AND TEST ACCURACY. COMPUTER ALGORITHMS USING RAW DATA WERE DEVISED, AND A DECISION ALGORITHM FOR APPLICATION BY COMPUTER WAS FORMULATED. THE ALGORITHM CONSISTS OF 10 RELATIONAL STATEMENTS FOR DETERMINING LD/NON-LD CLASSIFICATION. THESE STATEMENTS INCORPORATE DISCREPANCIES AMONG ABILITY AND ACHIEVEMENT TEST SCORES, EVIDENCE FROM OTHER TEST SOURCES, AND ORDINARILY CHARACTERIZED CLINICAL OBSERVATIONS. THIS ALGORITHM WAS REVISED TO NINE STATEMENTS TO TAKE ACCOUNT OF TEST RELIABILITIES AND TO REPLACE THE CONVENTIONAL SCORING METHOD OF THE WISCONSIN INTELLIGENCE SCALE FOR CHILDREN-REVISED WITH THE WITKIN (1974) SCORING SYSTEM. RESULTS INDICATED AN LD INCIDENCE OF 32 PERCENT FOR THE ADJUDICATED DELINQUENT SAMPLE COMPARED TO ONLY 16 PERCENT FOR THE NONDELINQUENT SAMPLE. THESE PREVALENCE VALUES INDICATE THAT FACTORS DIVIDING THESE BOYS INTO DELINQUENTS AND NONDELINQUENTS ARE ALSO ASSOCIATED WITH THE PHENOMENON OF LD AS DEFINED BY THE DECISION ALGORITHM. FUTURE RESEARCH PLANS ARE BRIEFLY OUTLINED. TABULAR AND GRAPHIC DATA AND REFERENCES ARE INCLUDED. (JAP)