The element mercury exists as inorganic, elemental, or organic species. Routes of exposure and toxicity in humans vary according to the species of mercury involved. Treatment of mercury poisoning generally requires the use of sulfhydryl bond-containing chelation agents, including the parenterally administered dimercaprol and its oral congeners. These oral chelators, meso-2,3-dimercaptbsuccinic acid and sodium 2,3-dimercapto-1-propanesulfonate, have numerous advantages over dimercaprol, including less toxicity. Although dimercaprol is contraindicated in organic mercury exposures, meso-2,3-dimercaptosuccinic acid and sodium 2,3-dimercapto-1 -propanesulfonate may be used to chelate alt species of mercury. Recent evidence suggests that their efficacy in organic mercury poisoning is uncertain. Curr Opin Pediatr 1999, 11:265–268 © 1999 Lippincott Williams 4 Wilkins, Inc.