Background: 'Hard to reach' young people are associated by virtue of their serious, multiple, and complex needs, the difficulty of delivering effective help to them, and their poor long-term outcomes. There is a lack of published evidence relating to the effectiveness of interventions directed at this group., Method: We review these concerns and the options available to service commissioners and clinicians seeking, if not an evidence-based approach then at least an evidence-oriented one. A mentalization-based multimodal intervention (AMBIT) is briefly described, proposing a new kind of specialist practitioner and taking a radically different approach to treatment manualization., Results: A brief description is given of the different settings in which AMBIT is currently being developed, deployed, and evaluated, and of lessons learned., Conclusions: AMBIT offers promise as an evolving 'open source' framework supporting development of evidence-based local practice in chaotic complex settings., (© 2012 The Authors. Child and Adolescent Mental Health © 2012 Association for Child and Adolescent Mental Health.)