Adverse drug reactions present a major clinical problem: for example, recent data show that poisoning accounts for about 4000 deaths each year in England and Wales alone. Furthermore, in addition to being a major cause of morbidity and mortality, adverse drug reactions can prevent effective drug therapy and, in extreme cases, can lead to the withdrawal of potentially valuable medicines. Pharmacological and clinical aspects of drug toxicity were reviewed at a symposium, Drug metabolism and toxicity, which formed part of the British Pharmacological Society meeting in Cardiff, UK, in July 2000. The meeting was organized by P. J. Nicholls and P. A. Routledge (Welsh School of Pharmacy and University of Wales College of Medicine, Cardiff, UK) and chaired by P. J. Nicholls.