Overall Abstract Aggression is a basic physiological trait of major importance in individual fitness through evolution. Its roles in defense, predation and survival in animals make it a probable adaptive trait that may be under stabilizing selection. In humans, aggressive behavior has some advantages in competition, reproduction and hierarchical dominance, but when expressed in the wrong context, it causes social impairment and may lead to injury or death. Aggressiveness is influenced by both genetic and environmental factors, each accounting for about 50% of the variance, according to twin and adoption studies. Although the genetic contribution is significant, human molecular genetic studies of aggression are still in an early stage and little is known about the specific molecular underpinnings of this behavior. The Aggressotype project (‘Aggression subtyping for improved insight and treatment innovation in psychiatric disorders’, www.aggressotype.eu), coordinated by Prof. Barbara Franke and funded by the EU FP7 Program, aims at investigating the biological basis of both the reactive (emotional, impulsive) and the proactive (instrumental, predator) presentations of aggression, combining work in humans and in animal models. Identification of the underlying genetic risk factors will eventually improve the targeting of aggression and the development of effective interventions. All four symposium speakers are members of the Aggressotype Consortium, and they will present the results of different studies that are part of this collaborative effort. Ditte Demontis (Aarhus University, Denmark) will explain the results of the largest genome-wide association study (GWAS) performed on conduct disorder (CD), a diagnostic category characterized by a persistent pattern of antisocial rule-breaking behaviours. The study is based on subjects from the large Danish iPSYCH sample combined with data from the ADHD cohorts collected by the Psychiatric Genomics Consortium. Noelia Fernandez-Castillo (University of Barcelona, Catalonia, Spain) will provide evidence for the involvement of a specific gene, RBFOX1, encoding a splicing regulator, in aggression, including results from genetics, neuroimaging and animal models. Yanli Zhang-James (SUNY Upstate Medical University, USA) will present an integrated and network-based analysis using previous data in human and rodent models to identify genes and pathways involved in aggressive behavior. These studies, based on GWAS data, transcriptome analyses in rodents and genes taken from the Online Mendelian Inheritance in Man (OMIM) database and knockout mice reports, point at usual suspects for this trait but also identify novel candidates. Finally, Jeffrey Glennon (Radboud University Medical Center, The Netherlands) will illustrate using inbred BALB/c mouse substrains (that differ in a relatively small number of mRNAs and CNVs) that aggressive behaviour is accompanied with an altered ability to learn from mistakes. This is associated with dysregulated GABAergic signaling, volumetric and white matter changes in the anterior cingulate cortex.