Research and treatment on juvenile offenders has been hampered by the lack of a precise operational definition of the construct "juvenile delinquency." The authors cite controversy in the literature to illustrate that the failure to replicate research findings and ultimately to develop successful treatment and rehabilitation programs for the juvenile offender is due to methodological imprecision, particularly the inadequate specification of the research sample. Methodological and treatment implications of this imprecision are discussed in light of recent "right to treatment" legislation. A model for specifying the characteristics of the research sample is proposed with the hope of improving the quality and comparability of future delinquency research.