Aggressive behaviour is common in forensic psychiatric settings. The aetiology of aggressive behaviour is multifactorial and can be driven by psychosis, impulsivity, psychopathy, intoxication, cognitive impairment, or a combination of all of these. Recognition of the different factors behind the aggression can inform medication selection and the relative need for specific environmental and behavioural interventions in a forensic psychiatric setting. Acute agitation needs to be managed quickly and effectively before further escalation of the behavioural dyscontrol occurs. Benzodiazepines and/or antipsychotic medications are often used and can be given intramuscularly to achieve a rapid onset of action. Available are intramuscular preparations of second-generation antipsychotics that have similar efficacy to lorazepam and haloperidol in reducing agitation, but are well tolerated and not associated with the extrapyramidal adverse effects, including akathisia, that can plague the older first-generation antipsychotics. The longer-term management of persistent aggressive behaviour can be quite complex. A major obstacle is that the causality of aggressive events can differ from patient to patient, and also from event to event in the same patient. For patients with schizophrenia and persistent aggressive behaviour, clozapine is recommended both for its superior antipsychotic effect and its specific anti-hostility effect. Mood stabilizers such as valproate may be helpful in instances of poor impulsivity and personality disorders. Other agents that have been successfully used include β-adrenoceptor antagonists (β-blockers) and antidepressants.