LITERATURE ON JUVENILE DELINQUENCY INDICATES THAT A SERIOUS MALE JUVENILE DELINQUENT USUALLY COMES FROM A DETERIORATED NEIGHBORHOOD, LOW SOCIOECONOMIC STATUS, AND SINGLE-PARENT FAMILY, OR A TENSE AND HOSTILE TWO-PARENT FAMILY HOME. THE SERIOUS DELINQUENT IS OFTEN ABSENT FROM SCHOOL AND SHOWS ASSAULTIVE TENDENCIES, DEFIANCE OF AUTHORITY, FEELINGS OF GUILT AND INADEQUACY AND IMPULSITY. HE IS EASILY INFLUENCED BY CERTAIN STIMULI, SUCH AS VIOLENCE ON TELEVISION, AND IS A REPEAT OFFENDER WHOSE CONTACTS WITH AUTHORITIES TEND TO REINFORCE HIS BEHAVIOR. AN OPERATIONAL DEFINITION OF SERIOUS JUVENILE DELINQUENCY INCLUDES (1) COMMITMENT OF VIOLENT OFFENSES AND/OR (2) REPEATED VIOLATIONS (FIVE OR MORE) WITH POTENTIAL FOR CAUSING SERIOUS INJURY TO ANOTHER PERSON. DATA FROM DYS FROM JANUARY 1976 TO MARCH 1977 WERE GATHERED TO DEVELOP A PROFILE OF THE SERIOUS JUVENILE OFFENDER POPULATION. A RANDOM SAMPLE OF 80 CASES NOT CONSIDERED SERIOUS BY DYS CASEWORKERS WAS COMPARED WITH ALL 100 CASES CONSIDERED SERIOUS DURING THE STUDY PERIOD. GROUPS WERE COMPARED WITH RESPECT TO SOCIAL FACTORS AND LEGAL VARIABLES. BIVARIATE ANALYSIS SHOWED THAT OLDER YOUTHS, BLACK YOUTHS, AND YOUTHS FROM SINGLE-PARENT FAMILIES WERE MORE LIKELY TO RECEIVE A MORE NEGATIVE LABEL BY JUVENILE JUSTICE DECISIONMAKERS. IN CONTRAST, MULTIVARIATE REGRESSION ANALYSIS SHOWED THAT THE ONLY SOCIAL VARIABLE ATTRIBUTABLE TO CASEWORKER IDENTIFICATION WAS FAMILY COMPOSITION (THAT IS, SINGLE-PARENT FAMILIES). IN TERMS OF LEGAL VARIABLES, SERIOUS JUVENILE OFFENDERS HAD MORE RECORDED OFFENSES, MORE SERIOUS OFFENSES, MORE VIOLENT OFFENSES, MORE SERIOUS LAST OFFENSES, AND MORE SERIOUS DISPOSITIONS, THAN OTHER OFFENDERS. IN BOTH GROUPS, RECIDIVISM WAS THE MOST SIGNIFICANT PROBLEM, ALTHOUGH IT WAS HIGHER IN THE SERIOUS OFFENDER GROUP. OVER THREE-FIFTHS OF THE SERIOUS OFFENDERS AND ONE-FIFTH OF THE GENERAL OFFENDERS HAD COMMITTED AT LEAST ONE VIOLENT OFFENSE. FOOTNOTES, TABLES, AND A REFERENCE LIST ARE INCLUDED. (AUTHOR ABSTRACT MODIFIED--CFW)