Self-poisoning is one of the commonest acute medical presentations in the UK. It is therefore not only important that clinical pharmacologists be aware of trends in the mortality and morbidity of self-poisoning, but also they be able to recognize the methodological limitations of the epidemiological data underlying them. One such limitation has been confusion over how various types of self-poisoning are described and subsequently registered. Three broad categories of self-poisoning (suicide, accidental self-poisoning and deliberate self-harm) will be defined in this review and the available information on them in the UK examined. Finally, paracetamol will be explored separately as an example bringing together issues from different self-poisoning categories.