Among psychiatric illnesses, genetically determined disorders usually have an early onset and a severe and complicated course. Gene-environmental interaction is of importance for aggressive impulsive behaviour. For example, alcoholism type II has a high family loading, a severe course, and is often associated with antisocial behaviour. In order to gain further understanding of aggressive and impulsive behaviour, genes determining serotonin metabolism, neurosteroids and carbohydrate metabolism should be of interest to investigate. Furthermore, modern brain-imaging studies will reveal the site of action of aggressiveness and impulsivity. Within brain regions of interest, biological studies will promote our knowledge of this deleterious behaviour.