The liquid-liquid extraction of Hg(II) from acidic chloride solutions has been studied using bis-2-ethylhexyl sulfoxide (B2EHSO) as an extractant. For comparison, extraction studies have also been carried out using di-n-octyl sulfoxide (DOSO) and diphenyl sulfoxide (DPhSO). The extraction data have been analysed by both graphical and theoretical methods taking into account aqueous phase speciation and all plausible complexes extracted into the organic phase. These results demonstrate that Hg(II) is extracted into xylene as HgCl2.3R(2)SO (where R2SO represents the sulfoxide). The equilibrium constant of the extracted complex has been deduced by non-linear regression analysis. The developed liquid-liquid extraction procedure has been applied for the recovery of mercury from the brine-sludge of a Chlor-Alkali plant.