Poisoning and overdose are an increasingly common problem in the UK, resulting in approximately 140 000 hospital admissions each year. Significantly more patients are assessed and discharged from Emergency Departments or managed in primary care. Accidental and deliberate self-poisoning may involve a variety of substances. This article aims to provide an overview of the common substances involved in poisoning and discusses the assessment and management of patients suffering from either an accidental or deliberate poisoning resulting in an overdose. The focus will be on ingested substances but it is important to recognise the dangers of inhaled poisons and dermal irritants.