Despite increasing interest in the mental health needs of children involved in the juvenile justice system, relatively little is known about the base rates of specific mental disorders in this population due to the absence of any national prevalence data. In 1992, two reviews of the existing empirical literature (Otto, Greenstein, Johnson, Friedman, 1992; Wierson, Forehand, & Frame, 1992) both concluded that relatively few well-controlled epidemiological studies had been conducted that could inform our knowledge of the prevalence of mental disorders in the juvenile justice system. Factors commonly cited that limited the generalizability of much of the existing research included: (a) failure to use random or comprehensive sampling procedures, (b) use of differing assessment instruments across studies or reliance on file information rather than structured diagnostic interviews, (c) assignment of only one diagnosis and failure to assess for multiple diagnoses/comorbidity, (d) samples being drawn from only one site or state, and (e) failure to consider how diagnostic rates might be affected by relevant demographic and historical variables such as age, gender, and length of detainment. Since the publication of these two reviews, few studies have been conducted that have significantly improved our knowledge of the prevalence of mental disorders in juvenile justice populations and national prevalence estimates of mental disorder still have not been established