Purpose To begin to develop an understanding of knowledge translation of early developmental crime prevention.Methods Involves a narrative review of experiments of early developmental prevention with measures of delinquency and criminal offending, and profiles two leading experiments, the Cambridge-Somerville Youth Study (CSYS) and the Montréal Longitudinal-Experimental Study.Results While the roots of early developmental crime prevention can be traced to studies of human development, experiments of preventive interventions are at the heart of knowledge translation and policy influence. This can be seen in the form of replications, the process of scaling up effective interventions for wider dissemination, and inspiration for prevention scientists to launch new and innovative experimentssometimes with the aim to improve upon past results. For example, far from curtailing policy interest in a developmental approach to delinquency prevention or dampening the need for prevention experiments, the harmful effects reported in the 30-year follow-up of the CSYS instead had an influence on some new longitudinal-experimental studies in developmental and life-course criminology.Conclusions New experiments are needed to continue to advance early developmental crime prevention, and further research is needed to add to our understanding of knowledge translation in this area.Keywords: developmental crime prevention; randomized controlled experiment; knowledge translation; public policy "… an evil man is rather like a sturdy boy, or a man of childish mind, and evil is simply want of reason at an age when it normally accrues to men by nature governed by discipline and experience of harm …"