This thesis explores the assessment and treatment of violence in adolescents with Developmental Disabilities (DD). Chapter 1 provides a summary of the background literature, and rationale for the thesis. A literature review exploring the availability and effectiveness of treatment with individuals with DD is conducted in Chapter 2, highlighting the scarcity of studies, particularly for adolescents with DD, and drawing tentative conclusions regarding treatment efficacy. Chapter 3 investigates the utility of The Structured Assessment of Violence Risk in Youth (SAVRY), in predicting violence risk in adolescents with and without DD in a forensic inpatient service. Significant but tentative findings suggest that the SAVRY is a strong predictor of violence in adolescents with DD, providing a promising avenue for research into the use of established adolescent violence risk assessments for individuals with DD. Chapter 4 critiques the How I Think Questionnaire (HIT), a psychometric measure for adolescents that assesses attitudes linked with violence. The HIT has undergone fairly stringent psychometric testing, but limitations are outlined and further validation is required. Chapter 5 presents a case study of the assessment and treatment process for an adolescent violent offender with DD. Chapter 6 discusses the findings of the thesis and consideration is given to the direction of future research.