Poisonings are a common problem. In 1995, over 2 million exposures were reported to American poison information centres alone. The majority of poisoning exposures can be treated without major therapeutic intervention. If therapy is indicated, it is usually in the form of gastrointestinal decontamination with activated charcoal, to prevent absorption of the toxin and the subsequent toxicity that may occur. In a limited number of cases, more aggressive life-support measures may be necessary to treat the adverse effects of poisons. Occasionally, that intervention may include the use of pharmacological antagonists, more commonly referred to as antidotes. According to the American Association of Poison Control Centers, the most commonly used antidotes are acetylcysteine, naloxone, atropine, deferoxamine (desferrioxamine) and antivenins. Overall, 17 antidotes account for 99% of all antidote use and those agents are reviewed in this article. With the exception of naloxone, most antidotes have pharmacological effects that are independent of their inherent antidotal properties. Therefore, antidotes should be used judiciously because their pharmacological properties may exacerbate pre-existing toxicity and only in rare circumstances are they used prophylactically. Some antidotes, such as digoxin-specific antigen binding fragments (digoxin immune Fab), are very expensive, and both the risk: benefit ratio and the associated cost should be considered before the antidote is administered. The principle aims are to "treat the patient, not the poison' and to do no harm to the patient. Antidotes should be used only when they are indicated and may help a patient.