This article describes a study examining the prevalence of mental illness, low intelligence, psychopathy, risk for reoffending, and criminogenic needs in 75 youth and young adult offenders in Victoria, Australia. Results suggest that the prevalence of mental illness and low intelligence is high in this population. Most (86 ) of the sample had likely Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Text Revision Axis I disorders (including mood, anxiety, substance use, eating, and psychotic disorders); 15 had a Full Scale Intellectual Quotient (FSIQ) below 70; and an additional 25.7 had an FSIQ in the borderline range. The majority (80 ) of the sample was considered to be at a high or very high risk of reoffending. The high prevalence of mental health issues found in this population highlights the need for comprehensive and multifaceted assessment, and for psychosocial treatment and management to be comprehensive, addressing clinical, criminogenic, and social domains.