THE FIRST COHORT, WITH 1,352 PERSONS, WAS BORN IN 1942; THE SECOND, WITH 2,099, IN 1949. DATA WERE COLLECTED ON REASONS FOR POLICE CONTACTS, SERIOUSNESS, AND PLACE OF RESIDENCE TO DETERMINE WHO WAS MOST LIKELY TO ENGAGE IN DELINQUENT BEHAVIOR, WHO WOULD CEASE DELINQUENT BEHAVIOR AS THEY GREW OLDER, AND WHO WOULD CONTINUE INTO ADULT CRIMINAL ACTIVITY. INTERVIEWS WITH 333 PERSONS FROM THE 1942 COHORT AND 566 PERSONS FROM THE 1949 COHORT FOCUSED ON PROCESSES WHEREBY JUVENILES WERE BROUGHT INTO CONTACT WITH POLICE AND ON REASONS FOR THEIR CURRENT ADULT BEHAVIOR. RESULTS SHOWED THAT ALTHOUGH OVER 80 PERCENT OF THE MALES HAVE THEIR NAMES IN POLICE RECORDS (IF MOVING VEHICLE VIOLATIONS ARE INCLUDED) AT SOME TIME IN THEIR LIVES, FEW HAVE A CONTINUING RECORD OF POLICE CONTACTS. NEVERTHELESS, AN EARLY POLICE CONTACT, DELINQUENT FRIENDS, PLACE OF RESIDENCE, AND OTHER VARIABLES WERE PREDICTIVE OF SERIOUS POLICE INVOLVEMENT DURING THE JUVENILE PERIOD (AGES SIX THROUGH 17), THE INTERMEDIATE PERIOD (AGES 18 THROUGH 20) AND ON INTO ADULT LIFE. DIFFERENCES BETWEEN AGE PERIODS SUGGESTS THAT HISTORICAL CIRCUMSTANCES PRODUCE PERIODIC CHANGE IN THE CIRCUMSTANCES GENERATING FREQUENT AND SERIOUS POLICE CONTACTS AMONG BOTH JUVENILE DELINQUENTS AND ADULT OFFENDERS. RESULTS ALSO SHOWED THAT DEFINITIONS USED AFFECT THE RESULTS PRODUCED. ALTHOUGH PERSONS IN THE INNER CITY AND ITS INTERSTITIAL AREAS WILL HAVE LENGTHIER AND MORE SERIOUS DELINQUENT CRIMINAL CAREERS THEN THOSE WHO LIVE IN AREAS OF BETTER SOCIOECONOMIC STATUS, CONTINUITY IN INDIVIDUAL CAREERS CANNOT BE PREDICTED. DATA DID NOT SHOW WHETHER EARLY ONSET OF POLICE CONTACTS MAY BE EXPLAINED BY EARLY ONSET OF DELINQUENT BEHAVIOR, CHANCE, OR EARLY IDENTIFICATION AND LABELING BY THE POLICE. FIGURES, FOOTNOTES, AND 13 CITY MAPS SHOWING DEMOGRAPHIC AND CRIMINALITY VARIATIONS, ARE INCLUDED. (CFW)