Violence is increasingly viewed as a public health issue that may be ameliorated by health-based interventions. The Healthy Brains and Behavior Study (HBBS) aims to identify environmental and biological risk factors for aggression in late childhood and to reduce aggression through psychological and nutritional treatments. Utilizing a cross-disciplinary collaborative research approach, the HBBS has both human and animal components. The human component has two stages consisting of risk assessment followed by treatment. The risk assessment is based on 451 community-residing children aged 11–12 years and their caregivers, during which genetic, brain imaging, neuroendocrine, psychophysiology, environment toxicology, neurocognitive, nutrition, psychological, social and demographic risk variables are collected. Children who met criteria (N = 219) for problematic aggressive behaviors were assigned to one of four treatment groups: cognitive-behavior therapy (CBT) alone, nutritional supplements alone, both CBT and nutrition, or treatment-as-usual. Treatment duration was 12 weeks and all children whether in treatment or not were followed-up at three, six, and 12 months. The animal component assessed the effects of dietary omega-3 fatty acids on the development of aggression. This study contributes knowledge on how biological factors interact with social factors in shaping proactive and reactive aggression and assesses the efficacy of treatment approaches to reduce childhood aggression. Copyright © 2013 John Wiley & Sons, Ltd.