[en] There are few regulatory and/or advisory criteria for mercury in contaminated soils, sediment, and waste. The most widely applied criterion for mercury in solid material is the performance of solid samples analyzed with leaching procedures developed by the US Environmental Protection Agency (EPA). These protocols, along with others, have been used to classify wastes under the Resource Conservation and Recovery Act (RCRA). Leaching results, expressed as the concentration of mercury in the laboratory-generated leachate, are compared to 200 μg/L. Results above this criterion are classified as having failed the RCRA ''toxicity characteristic.'' The 200 μg/L limit represents 100 times the Drinking Water Standard for mercury and requires the sample to contain at least 4 μg/g. The latter value is derived by multiplying the established limit, 200 μg/L, by the solution-to-solid ratio in the test, 0.02 L/g. Objectives of this study were to determine which forms of mercury in soil exhibit the highest leachability as analyzed by the EP and TCLP protocols and to determine whether headspace mercury vapor readings from soil samples are indicative of leaching performance. The four mercury compounds studied were elemental mercury (Hg⁰), mercuric sulfide (HgS), mercuric oxide (HgO), and mercurous oxide (Hg₂O). Whether the two leaching procedures yield equivalent results was also addressed