The aim of this project is to develop of an integrated and efficient and cost effective methodology for identifying the mercury species distributed according to groups of solubility (water-soluble, weak acids, organic acids, and aqua-regia) to be applied to characteristic soils of Mexico which are contaminated with mining or industrial wastes. The mercury speciation method developed in this study allows the identification of mercury species in contaminated soils using different extraction media, and identifying the following species: water soluble, elemental (amalgamated) mercury, exchangeable, strongly bounded (mineralized and Fe and Mn oxy hydroxides), organic mercury, mercury sulfides and residual. From these, some represent a potential risk due to their toxicity and ability to mobilize in the environment and to be assimilated by organisms: water soluble, exchangeable and organic species.