Any drug may produce unwanted or unexpected adverse effects. The World Health Organisation (WHO) defines an Adverse Drug Reaction (ADR) as: a response to a drug that is noxious and unintended and occurs at doses normally used in man for the prophylaxis, diagnosis or therapy of diseases, or for the modification of physiological function (WHO, 1972).ADRs are increasingly recognised as important causes of morbidity and mortality. It is estimated that one in sixteen acute general hospital admissions is attributable to adverse drug reactions. ADRs are also responsible for up to 10,000 deaths a year in the United Kingdom, and cost the NHS around £446 million each year (Pirmohamed et al, 2004).Psychotropic medications often have to be taken long-term, and because of their central action may produce a wide range of adverse effects. Several studies have shown that psychiatric patients' physical health tends to be worse than that of the general population, and that they may be less able to access medical services for their physical problems. These factors may put patients with psychiatric illness at increased risk of ADRs.Patients in forensic psychiatry units may be at still further increased risk of ADRs. In these settings, patients are more likely to have severe psychiatric illnesses and to demonstrate treatment resistance, which is thought to contribute to the high proportion of these patients who are prescribed high-dose and multiple psychotropic medications. For example, Acosta-Armas et al (2004) Recording adverse drug reactions in a forensic psychiatry unit: how can we improve standards?