A REVIEW OF THE LITERATURE AND AVAILABLE STATISTICS AS WELL AS STRUCTURED AND INFORMAL INTERVIEWS WITH KNOWLEDGEABLE JUVENILE JUSTICE PERSONNEL SHOWED THREE CRITERIA TO BE IMPORTANT IN THE DEFINITION OF THE SERIOUSNESS OF CRIME: VIOLENCE OR INJURY TO PERSONS, PROPERTY LOSS OR DAMAGE, AND CHRONICITY OR REPETITION OF OFFENSES. FROM CONCLUSIONS RELEVANT TO THE DEVELOPMENT OF A SET OF DEFINITIONS APPLICABLE TO JUVENILE CRIME, STUDY PARTICIPANTS RECOMMENDED THAT SERIOUS JUVENILE OFFENSES, BASED ON THE SELLIN-WOLFGANG SERIOUSNESS SCALE, INCLUDE HOMICIDE OR VOLUNTARY MANSLAUGHTER, AGGRAVATED ASSAULT, ARMED ROBBERY, EXTORTION, ARSON OF AN OCCUPIED BUILDING, AND OTHER OFFENSES. TO SYNTHESIZE EXISTING INFORMATION IMPORTANT TO ESTABLISHING RESEARCH PRIORITIES AND POLICY ORIENTATION, A FURTHER STUDY UTILIZED AN INFORMAL SURVEY, A COMPILATION OF DATA BEARING UPON JUVENILE CRIME OR OFFENDERS, A NATIONWIDE SURVEY OF STATE AGENCIES, AND A LITERATURE SEARCH. BECAUSE INFORMATION WAS INADEQUATE, RECOMMENDATIONS POINTED TO THE NEED TO EXPAND THE STATE SURVEY, EXPLORE JUVENILE COURT DATA, AND USE OTHER TECHNIQUES TO GATHER MORE USEFUL INFORMATION. A FURTHER STUDY HAD THE GOAL OF ASSESSING THE STATE OF KNOWLEDGE CONCERNING THE RELATIONSHIP BETWEEN SUBSTANCE ABUSE AND SERIOUS JUVENILE CRIME; NUMEROUS ABSTRACTS OF THE LITERATURE AND INDEXES COVERING CRIMINAL JUSTICE, PSYCHOLOGICAL, AND SOCIOLOGICAL STUDIES WERE SEARCHED FOR THE YEARS 1968 THROUGH 1978. FINDINGS INDICATED THAT MUCH OF THE SERIOUS CRIME COMMITTED BY JUVENILES IS INDIRECTLY ASSOCIATED WITH SUBSTANCE ABUSE; CONSEQUENTLY, EFFORTS TO PREVENT SERIOUS JUVENILE CRIME MUST ALSO PREVENT AND CONTROL JUVENILE SUBSTANCE ABUSE. GRAPHS, CHARTS, TABULAR DATA, AND FOOTNOTES ARE INCLUDED. APPENDED INFORMATION PROVIDES REFERENCES, TABULAR DATA, A GLOSSARY, A LIST OF PARTICIPANTS IN THE NATIONAL JUVENILE JUSTICE SYSTEM ASSESSMENT CENTER, AND SUPPLEMENTARY DISCUSSIONS.