THERE IS RECURRING EVIDENCE FOR CHARACTERISTICS AND SITUATIONS EMERGING DURING VARIOUS PHASES OF DEVELOPMENT WHICH DISTINGUISH EXTREME DRUG USERS FROM OTHERS, AND ALSO DISCRIMINATE BETWEEN THOSE HEAVILY DRUG-INVOLVED AND OTHERWISE DELINQUENT IN CONTRAST WITH OTHERS. CONTROLLING FOR MAJOR SOCIOECONOMIC VARIABLES, IT IS POSSIBLE TO IDENTIFY FAMILIAL AND PERSONAL FEATURES WHICH HAVE PREDICTIVE POWER. WITHIN THE FAMILY, THERE ARE ALSO STRIKING DIFFERENCES BETWEEN THOSE BOTH DRUG-INVOLVED AND DELINQUENT AND THEIR SIBLINGS. IT CAN BE INFERRED THAT THE GREATER THE PRESENCE OF ANTISOCIAL AND DRUG-CENTERED ACTIVITIES COUPLES WITH UNCONVENTIONAL VOCATIONAL AND SOCIAL INTERESTS, THE MORE NOTICEABLE ARE OTHER DISCRIMINATING FEATURES IN BACKGROUND AND PERSONALITY. SOME VARIABLES ARE VISIBLE OVER LONG DEVELOPMENTAL PERIODS, OTHERS SEEM LIMITED TO DEVELOPMENTAL EPOCHS. DISCRIMINATING VARIABLES AT ONE OR ANOTHER STAGE INCLUDE EXTREME PARENTAL DRUG USE, CRIMINALITY AND MARITAL INSTABILITY, INFANCY PROBLEMS (INCLUDING MATERNAL CHILD BEARING DIFFICULTIES, INFANT ILLNESS), PERCEIVED INADEQUACY IN PARENTING, ILLNESS THROUGH CHILDHOOD AND AT PRESENT, PROBLEMATIC PEER RELATIONS DEFINED BY OVERRESPONSIVENESS, LACK OF AFFECTION OVER SEVERAL GENERATIONS, EARLY AND CONTINUING SCHOOL PROBLEMS, EARLY EMERGING TRUANCY AND DELINQUENCY, AND MORE SEXUAL ACTIVITY. IT IS NOT SUGGESTED THAT ALL OF THESE CHARACTERIZED ANY GROUP OR PERSON; NO ONE MOLD STAMPS ALL EXTREME DRUG USERS OR DELINQUENTS USING DRUGS. IT IS LIKELY THAT MULTIPLE PATTERNS INCLUDING THESE COMPONENTS AND OTHERS APPEAR DURING DEVELOPMENT. SUGGESTIONS FOR FUTURE RESEARCH ARE PROVIDED, ALONG WITH A BIBLIOGRAPHY. (KBL)