In Swedish child and adolescent psychiatry there is a more than 60-year long tradition of using longitudinal methods in research on juvenile delinquency. Since the 1940's, results have been presented using either prospective or retrospective longitudinal designs for this purpose. Starting from genetics as scientific paradigm, new approaches including neuropsychiatry and social psychiatry showed the need for a multidisciplinary view at the border between medicine and behavioral sciences. Both Swedish and international research in the area has clearly demonstrated that factors relating to gender, maturation, resilience vs. vulnerability, the mental health of the parents, the social network and the organization of the school are of importance when trying to understand, prevent and treat juvenile delinquents. The challenge presented to today's and future researchers is to understand how the complexity of the modern western society will impact already established knowledge.