The definitional process cannot be considered apart from the issues associated with the selection of individuals who fit the definitions, because the category is socially created based on practical concerns, political philosophies, and public opinion. Most definitions make both the type of offense and some degree of repeat offending a characteristic of the serious juvenile offender. Zimring lists homicide, rape, aggravated assault, and robbery as serious offenses. The report by Smith and others for the American Justice Institute (AJI) use two major criteria for determining serious offenses: violence and property loss. The AJI definition also includes the illegal sale of dangerous drugs. Using the Sellin-Wolfgang scale, the cumulative seriousness of the record is the determining factor in the definition. The serious juvenile offender is viewed as one who has at least one recorded offense that inflicted substantial harm or one who has an official record containing offenses that cumulatively involve the infliction of substantial harm. State laws give meaning to the term by defining youths eligible for adjudication in criminal courts and youths given harsher sentences within the juvenile justice system. Medical model concepts focus on the treatment problem the offender presents. The practical implications of trying to define and identify serious juvenile offenders are illustrated by the issues raised in the Violent Juvenile Offender Program, a $4 million federally funded research and development program lasting 36 months. A figure, 17 notes, and 31 references are provided.