Emergency physicians are familiar with British anti-Lewisite (BAL) because it is a heavy metal-chelating agent that is recommended in some cases of metal poisoning, especially arsenic. Although there are more modern chelating agents, the fact that BAL is still recommended and stocked by hospital pharmacies more than 60 years after its initial synthesis is itself remarkable. During World War II, BAL minimized the risk to the Allied infantry of injury or death from Lewisite, a very potent arsenic-based chemical warfare agent. Once developed, BAL revolutionized the treatment of heavy metal poisonings, both accidental and iatrogenic (eg, toxicity from treatment of arthritis with gold salts). In 1951, BAL was used to treat Wilson's disease with striking success. Today, BAL might again become prominent should terrorists or governments use Lewisite against civilians or military forces.