There has been much interest in the role of serotonin in aggressive behavior during the past two decades, but no simple one-to-one causal relationship has been found between this biological variable and aggression. The influence of serotonin is best analyzed within a broader framework that includes consideration of its role in the inhibition of impulses, the regulation of emotions and social functioning, domains that are closely linked to aggression. Impulsivity and strong emotional states often accompany violent acts. Aggressive individuals are likely to experience general difficulties with impulse control and emotional regulation, and they show impaired social cognition and affiliation. Serotonergic dysfunction will influence aggression differently, depending on the individual's impulse control, emotional regulation, and social abilities. Yet, aggressive acts occur in a broader social context. As such, serotonergic function has an effect not only on the individual but also on the group dynamics, and it is in turn influenced by these dynamics. Whether aggression will occur when serotonin dysfunction is present will depend on individual differences as well as the overall social context.