THE STUDY SAMPLE CONSISTED OF ALL MALE JUVENILES FROM CONTRASTING ECOLOGICAL AREAS IN SYDNEY, AUSTRALIA, WHO WERE INSTITUTIONALIZED DURING 1971-1972: 48 FROM AREAS OF INDIVIDUALIZED SOCIOECONOMIC ALIENATION, AND 71 FROM AREAS OF LOW SOCIOEDUCATIONAL STATUS. A TOTAL OF 26 VARIABLES UNDER FOUR HEADINGS WERE ANALYZED: RECORD OF DELINQUENCY, PERSONAL BACKGROUND, FAMILY CHARACTERISTICS, AND COURT ACTION/INSTITUTIONAL COMMITMENT. ANALYSIS OF DATA FOLLOWED THE PROBLEM-CLASSIFICATION MODEL AND NONPARAMETRIC STATISTICAL TESTS WERE USED. A NUMBER OF VARIABLES WERE FOUND TO DIFFERENTIATE BETWEEN THE TWO GROUPS OF OFFENDERS. SIGNIFICANTLY MORE OFFENDERS NOT MOTIVATED BY GAIN COME FROM ALIENATION/MALADAPTIVE AREAS AND HAVE A CRIMINAL RECORD OF SUCH OFFENSES AS ASSAULT, MALICIOUS DAMAGE, AND SEX AND DRUG OFFENSES. MEMBERS OF THIS GROUP WERE ALSO MORE LIKELY TO ACT ON THEIR OWN AND TO ESCAPE REPEATEDLY FROM LEGAL CUSTODY. THE ALIENATION GROUP HAD SIGNIFICANTLY MORE NEUROPSYCHIATRIC CONDITIONS, AND SIGNIFICANTLY MORE OF THEM CAME FROM BROKEN HOMES, HAD SMALL FAMILIES, AND RESIDED WITH OTHER THAN FAMILY MEMBERS OR RELATIVES. ALIENATION AREA JUVENILES ALSO HAD SIGNIFICANTLY MORE PROBATIONARY PERIODS. WHILE THESE FINDINGS DO NOT IDENTIFY MUTUALLY EXCLUSIVE GROUPS OF JUVENILE DELINQUENTS, SIGNIFICANT DIFFERENCES DO EXIST BETWEEN THE TWO GROUPS UNDER STUDY. IT IS CONCLUDED THAT AN ECOLOGICAL APPROACH TO DELINQUENCY TYPOLOGY COULD MAKE A SUBSTANTIAL CONTRIBUTION TO CRIMINAL THEORY AND PRACTICE IF DEVELOPED TO ITS FULL POTENTIAL. REFERENCES ARE PROVIDED. (JAP)