Of the 136 youth for whom substance-abuse diagnoses were available, 65 percent also had a co-occurring mental disorder. Mental disorders included depression and generalized anxiety disorder, conduct disorder, and attention deficit/hyperactivity disorder (ADHD). Both male and female detainees had high levels of substance abuse and dependence. Forty-four percent of detainees screened for substance use were identified as being at risk for substance abuse or dependence. Regarding offenses, the majority of youth had prior offending histories and court involvement. Domestic-violence offense rates were notable, with approximately one-third of the youth having a domestic violence charge. These findings highlight the need for effective, integrated, family-based treatment models that can address multiple co-occurring substance-use and mental disorders as well as abusive behavior against intimate partners. Intervention models should involve multiple child-serving systems, including juvenile justice, education, mental health, and substance abuse. For the study period of May 2003 to March 2005, screening of 1,477 youth for drug and alcohol use was done in the Cuyahoga County Juvenile Detention Center in Ohio. The screening included all youth who had stayed one night in the detention center, were 12-18 years old, and were arraigned on a new charge. Of the 1,477 youth screened, 211 were referred to the Strengthening Communities for Youth (SCY) project, a system of care for substance-abusing youth. Over a 22-month period, a sample of 118 males and 22 females were comprehensively assessed and treated. Data were obtained for arraignment charges, substance-use patterns and disorders, mental disorders, and co-occurring disorders. 5 tables and 27 references