OF 411 BOYS FROM SIX SCHOOLS ORIGINALLY CONTACTED AT THE AGE OF EIGHT, 389, OR 95 PERCENT, WERE FOLLOWED UNTIL AGE 18 OR 19. OF THESE, 30 PERCENT HAD ACQUIRED A CRIMINAL RECORD, A FIGURE CORRESPONDING TO THAT FOUND BY OTHER RESEARCHERS IN SIMILAR NEIGHBORHOODS. THIS STUDY USED IN-DEPTH INTERVIEWS AND PSYCHOLOGICAL QUESTIONNAIRES TO PROBE THE DIFFERENCES IN BEHAVIOR AND ATTITUDE BETWEEN DELINQUENTS AND NONDELIQUENTS. IT WAS FOUND THAT THE DELINQUENTS CHANGED JOBS MORE FREQUENTLY AND RARELY TOOK EMPLOYMENT WHICH REQUIRED TRAINING. THEY SMOKED MORE, GAMBLED MORE, HAD MORE ACCIDENTS, BROKE MORE TRAFFIC LAWS, WENT OUT MORE, HAD MORE SEXUAL EXPERIENCES, AND WERE MORE OFTEN PROMISCUOUS. ESPECIALLY AMONG THOSE WITH MULTIPLE CONVICTIONS, AGGRESSIVENESS AND GENERALLY TROUBLESOME BEHAVIOR HAD BEEN EVIDENT SINCE AGE 10 OR BEFORE. CONVICTION CAREERS PROVED TO BE PERSISTENT; TWO-THIRDS OF THOSE WITH TWO OR MORE JUVENILE CONVICTIONS HAD ONE OR MORE CONVICTIONS AS AN ADULT. OF THE 18 CONVICTED UNDER AGE 13, HALF WERE RECONVICTED BY AGE 19 OR 20. MOST OF THE JUVENILE OFFENSES WERE COMMITTED 'FOR FUN' OR BECAUSE OF GROUP PRESSURE. BY AGE 18, VANDALISM AGAINST PROPERTY WAS OFTEN DONE 'FOR FUN,' BUT BURGLARY AND LARCENY WAS USUALLY PREMEDITATED AND DONE FOR RATIONAL ECONOMIC REASONS. SOME EVEN SPOKE OF THESE ACTS AS 'WORK.' RECEIVING PROPERTY SUSPECTED TO BE STOLEN, OR 'BUYING CHEAP,' WAS COMMON AMONG BOTH DELINQUENTS AND NONDELINQUENTS. AUTO THEFT WAS APTLY CALLED 'JOY RIDING' AMONG THE YOUNGER BOYS, BUT WAS CONSIDERED 'BORROWING' BY THE OLDER GROUP. FAMILY HISTORY HAD A GREAT DEAL OF INFLUENCE ON DELINQUENT BEHAVIOR. OFFICIAL MEASURES OF INTERVENTION OFTEN MADE THE BEHAVIOR WORSE. IMPLICATIONS OF THESE FINDINGS, POSSIBLE POINTS OF INTERVENTION, AND POSSIBLE MEANS OF INTERVENTION ARE DISCUSSED. APPENDIXES GIVE THE TECHNIQUES USED TO SECURE AND CONDUCT INTERVIEWS, SELF-REPORTED DELINQUENCY SCORES AT AGE 18, DETAILED COMPARISONS OF SUBGROUPS IN RESPECT TO PERCENT DELINQUENT OR RECIDIVIST, AND LISTS OF FACTORS MEASURED BY DIFFERENT TESTS. STATISTICAL FINDINGS ARE GIVEN IN A SERIES OF TABLES.